Help ! cloudy water - what do i do ???

[Darwin]

Hi,

I started up a 20G tank about 10 weeks ago and started to have troubles a couple of weeks ago. I am afraid that I am making mistake after mistake even though I am now trying to research info rather than just trusting the LFS.

Anyway...this morning my last clown loach died (the other one died a week ago) after suffering from bloating for a week. I hadn't moved him to the hospital tank (probably very stupid) because I didn't want to stress him and the other fish (two cories and four giant danios) were leaving him alone in his cave. This morning when I found him dead, the water looked a little bit cloudy so I did a 25% water change (I have been doing 25% water changes 2-3 times a week recently)

Then I dropped home at lunch and the tank was soooo cloudy you could hardly see the fish, so I did another 40% water change and moved the fish to the 5G tank temporarily. When I got home from work, it was even worse - it looked like a tank of milk.

My parameters yesterday were ammonia 0, nitrite 0, nitrate 5-10 ppm, pH 6.8. I didn't measure any water parameters until this evening - after I had already done the 25% and 40% water changes but when I measured it after i got home from work, they were ammonia 0.25 ppm, nitrate 0, nitrate 10 ppm, pH 7.2. However, I didn't add any pH down (which i have been doing) to the water today when i did the changes and my tap water is pH 8 (but really soft; I have to add aquarium salts to get the GH up to around 5). So it is likely my pH was lower than 7.2 before the water changes.

I have now done an even bigger water change (80%) and added bicarb as well as aquarium salts to increase the kH. Up till now I hadn't thought much about kH (which was usually around 1-2, but after reading some of the threads I was wondering if that might be the problem. Now my KH is 4 and GH is 6 and my pH is around 7.4 ( I have put the fish back in the main tank because the ammonia content in the 5G had already increased to 0.5 ppm).

What I was wondering was - why the cloudiness; does it sound like i have killed my bio-filter ? And if so, what should I be doing now for the fish I currently have. Have I done the right things - or have I made it even worse (which is all i seem to be doing lately).

Any advice would be very very appreciated.

[fish_freak]

Most likely a bacteria bloom. For soom reason they seem real common with that size tank. If thats what it is then do nothing you just have to let the tank sit and it will clear up. I battled this for months and months and finaly when I listened and just left the tank alone for like a month no water changes or anything. Another thing that might help is adding some biological media to your filter. It gives the bacteria a place to go. How r your other fish?

[budrecki]

Ok. Start at the begining. You have ammonia you you are cycling for some reason.

Water parameters?

Why are you adjusting your ph?

What kind of filter do you have?

[Roan Art]

Ok. Start at the begining. You have ammonia you you are cycling for some reason.

Water parameters?

Why are you adjusting your ph?

What kind of filter do you have?
Also, why are you using salts to up your GH? What kind of salts? Please tell me it's not Epsom salts.

Test your KH, *that* is the important number. Not the GH. Please test for both in the tap water and the tank water and post both here. The KH is most important and if you have soft water as you say, I really really need that number from the tap ASAP.

Do not add salts. In fact, remove the salts with water changes. You don't want nor need that.
Do you know how much salt you have put in your tank so far?
Did you mix it *thoroughly* with a lot of tank water?
Do you have any other bottom feeders besides the clown loaches?

Thanks!

Roan

[Darwin]

The KH from my tap is 2. The salts I have been adding are aquarium salts that my LFS told me to add (not epsom salts). The container doesn't say what's in there but when i add it, it doesn't seem to do anything to the KH - just ups the GH.

As for bottom feeders; I have two two bronze cories in there.

This morning the tank doesn't look cloudy anymore - but i am measuring 0.5 ppm ammonia (nitrite 0, nitrate about 5 ppm, pH 7.2). I haven't seen ammonia in this tank for weeks now, so I think i must have stuffed up my biofilter (ceramic noodles in an Aquaone AR620 filter in tank lid thing). Oh and I am using dichlorinater/dechloraminator - my water supply doesn't use chloramines though.

Help please - I really don't want to kill anymore fish.

[Darwin]

Oh - and the reason I am adjusting my pH is because my tap water is pH 8 and my LFS told me that I was doing too frequent water changes - making the tank too alkaline. I was doing water changes twice a week because my clown loaches were sick, possibly from effects of the nitrogen cycle but i didn't get a complete test kit when i set up the tank (LFS said no need). Anyway the LFS said that I was making the tank too alkaline with the water changes and I need to use pH down to get around this.

[Darwin]

Sorry - about the bits and pieces reply. I keep realising I haven't answered all your questions. The KH in my tank is now 4 (I added bicarb yesterday when i did the MASSIVE water water change).

[Roan Art]

Okay, Darwin, you have a real problem so hold the phone while I consolidate everything into one response.

Roan

[Roan Art]

The KH from my tap is 2. The salts I have been adding are aquarium salts that my LFS told me to add (not epsom salts). The container doesn't say what's in there but when i add it, it doesn't seem to do anything to the KH - just ups the GH.
Okay, stop with the salts. They are not helping the situation at all and could make things worse.

Your KH is too low and that's dangerous. I have the same KH. I hate it ;)


As for bottom feeders; I have two two bronze cories in there. Okay, do you know how much salt you've put in?


This morning the tank doesn't look cloudy anymore - but i am measuring 0.5 ppm ammonia (nitrite 0, nitrate about 5 ppm, pH 7.2). I haven't seen ammonia in this tank for weeks now, so I think i must have stuffed up my biofilter (ceramic noodles in an Aquaone AR620 filter in tank lid thing). Oh and I am using dichlorinater/dechloraminator - my water supply doesn't use chloramines though.Any ammonia readings from the tap at all?


Help please - I really don't want to kill anymore fish.We'll work this out together, kay?


Female Oh - and the reason I am adjusting my pH is because my tap water is pH 8 and my LFS told me that I was doing too frequent water changes - making the tank too alkaline. I was doing water changes twice a week because my clown loaches were sick, possibly from effects of the nitrogen cycle but i didn't get a complete test kit when i set up the tank (LFS said no need). Anyway the LFS said that I was making the tank too alkaline with the water changes and I need to use pH down to get around this. Don't adjust your pH, it causes instability and a stable pH is more important than a low one. I've seen much worse than a pH of 8. Fish adjust to pH, they don't adjust to constant changes as well.


Sorry - about the bits and pieces reply. I keep realising I haven't answered all your questions. The KH in my tank is now 4 (I added bicarb yesterday when i did the MASSIVE water water change). GOOD! Now you're cooking! Those were the two correct things to do.

At any point do you know if your pH dropped to 6? If you do not have ammonia in your tap water, and your pH did a sudden dip, then with that KH of 2 I would have to conclude that your pH crashed. In otherwords your KH went to 0 and there was no bicarbonate available for bacterial use. The bacteria stop mulitplying and eventually die off. Your tank begins to cycle again, but only if the KH is replenished.

Anything 3 dKH and under needs to be monitored closely. It will raise your pH slightly, but you need to add some crushed coral to your filter to buffer the KH up to at least 4. Bicarb is a short-term solution and should only be used to buffer until the coral starts to help.

My KH is also 2, pH 7.4 out of the tap. With coral I get 3-4 dKH and pH 7.6-7.8, so it doesn't buffer *that* high. It will still be fine for the fish.

So, get some coral -- aragonite sand/coral mix works fastest -- put it in a sock or nylon (pantyhose toe) and stick it in your filter. It will take some time for it to dissolve in your high pH. Possibly a week or two. Use baking soda and maintain at 4 dKH until you see it rise to 5 dKH on its own. Do a 50% water change and test it. If it's at 3 dKH, don't add baking soda and continue to monitor it. Add more coral/aragonite if need be. Try to get it to buffer to 4 dKH.

I'm going to cover the ammonia, nitrites and nitrates stuff in the next post.

Roan

[Roan Art]

Had to get the kids to bed and they aren't going quietly :)

Okay, went back and reread what you had done and where the tank was now. It seems to be getting back on track and you had already figured out that your KH was the problem and not the GH. Good going and I should have noted that earlier.

The cloudy water was bacterial bloom from the crash, as you suspected.

Clown loaches and other bottom feeders are pretty sensitive to water quality. You mentioned your loach was bloated, and I thought he might have gotten a dose of Epsom salts. Also possible that the aquarium salt may not have dissolved fully and he might have eaten some. That happens and I suspect I lost a cory cat to that type of thing. I know better now.

Try to keep the ammonia down to .25 and expect a nitrite spike soon. Don't worry too much about the salt for now. It will actually help with the nitrite toxicity when they show up.

Water changes to keep the nitrites and ammonia in check and everything should work through the mini cycle quickly.

Let me know if I missed anything, kay?

Roan

[Darwin]

thank you so much for your time Roan - it is VERY much appreciated.

Ok. this time i'll try and cover all your questions in the one response.

Salt: I put in two teaspoons for the whole tank (20G) and a proportion thereof when i do a water change (25% water = 1/2 teaspoon). This is the amount the LFS told me to put in. It seems to raise the GH from about 3 to 5. Current GH is 5.

Ammonia: There is no ammonia in the tap water. The tank is testing about 0.5 ppm ammonia.

Adding bicarb and doing the MASSIVE water change: Thank you, I am glad I got something right !! I feel like absolute dunce at the moment.

Did the pH drop to 6 ?: I don't know because I freaked out when it got really cloudy and didn't check the pH until AFTER I had done the 25% and 40% water changes (stupid, but i know better for next time). But the night before the tank turned to milk the pH was 6.8 - so i would say it is possible that it got to 6.

KH: I am going to get some coral today, and am immediately stopping messing around with using pH down in the tap water. I think I might try a different LFS.

It sounds like I have lost my biological filter and will be starting from scratch cycling the tank...at least this time I actually have a complete test kit.

I just want to say again how much I appreciate you helping me out.

[Darwin]

Just one question before I head out to get some coral - how much do I need to put in ?

I'll keep up the frequent water changes and minimum daily testing (probably more often considering how worried I am about it). No more pH down, but I guess until the coral gets going I should continue to add bicarb to keep the KH at 4; is that right ?

Thanks

[Roan Art]

Just one question before I head out to get some coral - how much do I need to put in ?Just a handful or so. I like using pantyhose because I think the water flows through better and it doesn't get as much of a stinky mulm build-up like socks do.

Ask the LFS if they will just give you some. Sometimes they feel gracious ;)


I'll keep up the frequent water changes and minimum daily testing (probably more often considering how worried I am about it). No more pH down, but I guess until the coral gets going I should continue to add bicarb to keep the KH at 4; is that right ?Yes on all counts. Once your KH rises to 5 on its own, 50% water change and check it. If it's at 4 or 5 without baking soda, then you probably won't need the bicarb any more. You do need to keep an eye on it though.

Test your tap periodically as well for all parameters. Water companies are always futzing with things and I don't think Darwin is any different in that respect :D You never know when they might start throwing chloramine at you.

Actually, shoot, it's summer there, right? Ach, okay, most places (here anyway) use chlorine in the summer and chloramine in the winter. Contact your water department and ask them what their schedule is. See if you can get a water report as well. You might start seeing chloramine in a few months when winter comes to Aussieland.

Roan

[Darwin]

Thanks again. From what I understand in Australia the main cities use chlorine and rural areas use chloramine but they don't change according to the season (maybe because the seasonal temperature differences aren't as big as in the US).

I'll let you know how I go...all things going well I'll be asking for advice after my tank has cycled, as to what fish would mix well with the four giant danios and two cories !!! Not Clown Loaches in a 20G (I have learnt my lesson there).

[Roan Art]

thank you so much for your time Roan - it is VERY much appreciated.Not a problem at all.


Salt: I put in two teaspoons for the whole tank (20G) and a proportion thereof when i do a water change (25% water = 1/2 teaspoon). This is the amount the LFS told me to put in. It seems to raise the GH from about 3 to 5. Current GH is 5.Okay, that should help with the nitrites.


Ammonia: There is no ammonia in the tap water. The tank is testing about 0.5 ppm ammonia. Okay, try to get that down to .25 if you can. Never let it get above .5, though.


Adding bicarb and doing the MASSIVE water change: Thank you, I am glad I got something right !! I feel like absolute dunce at the moment.You shouldn't. I crashed my own tank a few weeks ago two days into a cycle. Wasted two packages of 90g Bio Spira and almost an entire box of baking soda trying to re-establish it.

The water department had done another dance on my tap water again. KH was at 3 last I had checked, just a few days before, and then it was 2 dKH. Coral hadn't had time to dissolve and the Bio Spira just ate up all the bicarb I had put in. Massive water changes to fix it, more soda, more Bio Spira and I finally had it under control. Didn't bother the dang fish at all.

So, it happens even when you know it can happen :)


Did the pH drop to 6 ?: I don't know because I freaked out when it got really cloudy and didn't check the pH until AFTER I had done the 25% and 40% water changes (stupid, but i know better for next time). But the night before the tank turned to milk the pH was 6.8 - so i would say it is possible that it got to 6.Nod. You did what anyone would do. Save the fish first, heck with the test. I would have done the same.


KH: I am going to get some coral today, and am immediately stopping messing around with using pH down in the tap water. I think I might try a different LFS.Sometimes they *do* get things right. Best thing to do is either know more than they do, or take what they tell you and verify it before doing it.


It sounds like I have lost my biological filter and will be starting from scratch cycling the tank...at least this time I actually have a complete test kit.Yes, but you still have *some* bacteria, so it shouldn't take to long to get it re-established.


I just want to say again how much I appreciate you helping me out.It's definitely not a problem. I like to help when I can.

Roan

[Darwin]

Just letting you know - I picked up some crushed coral today and put a handful in some pantyhose, rinsed it in dechlorinated water and put it in the filter.

Did a water change this evening ammonia is between 0.25 and 0.5 ppm.

The fish are looking settled again (the danios are back to their usual busy selves and their appetite is well and truely back to normal), so hopefully they'll bounce back from this horrible experience !

[Roan Art]

Unless something unforeseen happens, I think they will ;)

Keep us posted, please.

Roan

[goldfishPOGO]

I actually bought some Accu-Clear from a local Aquarium. You have to put 2 drops for every gallon of water, and it started working for me in less than half an hour. I didnt think it would work- but it works GREAT

[Roan Art]

I actually bought some Accu-Clear from a local Aquarium. You have to put 2 drops for every gallon of water, and it started working for me in less than half an hour. I didnt think it would work- but it works GREAT
Most of the time using a product such as Accu-Clear will only mask the problem, not solve it.

The best thing to do is find out *why* you have cloudy water and deal with that.

Roan

[Darwin]

Hi,

Just an update;

All is going well in the tank and the water has stayed clear. Have been keeping ammonia below 0.5 ppm with daily water changes and today the ammonia started dropping without a water change, to between 0 and 0.25 ppm .

Interestingly, I haven't seen any nitrite at all when testing and up until today nitrate was also 0. So I was worried that the cycle wasn't progressing. But today the nitrate is 0 - 5 ppm, so the cycle seems to be going o.k. Maybe the nitrite to nitrate bacteria must have survived the crash better than the ammonia to nitriate bacteria and that's why nitrite has stayed at 0. I am maintaining KH at 4 (still adding a bit of bicarb with the water changes).

I agree with Roan about finding out why you have the problem, hopefully now I can prevent it from happening again !

[Roan Art]

That's great, Darwin! A little worrisome that you show no nitrites, but since your tank had been cycled before, probably not unusual.

Hope all continues to go well
Roan

[happychem]

I hate to be contradictory after 2 pages of advise and plenty of corrections, but there's nothing wrong with a KH of 2 degrees, unless you're injecting CO2. It simply means that you can't be slack on water changes. Our tap KH is often lower, sub-1 degree (roughly 10 ppm) and my pH is rock solid.

Shoot to do a 50% change weekly, minimum (which could be 2 30% changes or 3 20% changes, whichever regime is most convenient). Consider that a 5 gal bucket will give you a 25% change in about 10 minutes. I've actually started doing daily changes on my 18 gal tank after work. It's dead easy and takes no time, and I've never seen the colour and activity that my fish are showing. Anecdote aside, leave the crushed coral in the filter, it won't hurt anything (dissolution is slow) and will be a good failsafe, but stop adding bicarbonate.

The amount of salt that you were adding was negligible. It's the "tonic" amount recomended by lfs salespeople (not to be confused with enlightened aquarists working at lfs') because it won't do any harm (nor any help).

The pH-Down is the most likely culprit for your crash. Always be very wary of making any pH mods, consider a strong acid titration of a weakly-(or non-)buffered solution, remember what happens to pH at the end-point? (it takes a rapid dive for the non-chemists) pH - KH in effect - is not something to be monkeyed with by the faint of heart. Any modifications have to be made very carefully and consistently, and only for very special reasons - like wild caught specimens or breeding.

Finally, what's the colour and turbidity of a saturated ammonia solution? Crystal clear, but it will kill pretty much anything in it.

Clarity is not an indicator of water quality. In the event of a bloom such as that the best course of action is to aerate (something I seldom advocate) or lower the water level so that the filter splashes. The shearing force between filter return and water surface is excellent for gas exchange. Your only real concern during a bloom as severe as you described is O2 content. With that high a bacterial density the O2 demand spikes. If I had to guess, I'd say that the pH-Down killed or seriously distrupted your free floating fauna resulting in the bloom and the resulting O2 depletion killed your nitrifying colonies.

[Roan Art]

I hate to be contradictory after 2 pages of advise and plenty of corrections, but there's nothing wrong with a KH of 2 degrees, unless you're injecting CO2. It simply means that you can't be slack on water changes. Our tap KH is often lower, sub-1 degree (roughly 10 ppm) and my pH is rock solid.Ah! But happychem, I disagree!

In a cycled tank, yes, a KH of 2 is more than fine. I have several tanks with a KH of 2. What I have found, however, is that when I am cycling a tank with a KH that low, I will crash if I do not either water change or add baking soda beforehand. It's happened to me a couple of times now.

Maybe because of an "accelerated" cycle -- like when you use Bio Spira, filter media, or are "recycling" for whatever reason. Is it not possible that, given that many of the needed bacteria are already present and there is an abundance of "food" and space, that they mulitply more rapidly than normal? Thus depleting the bicarbonate at a much faster rate than normal?

Not possible? Yes? No? Yer off yer rocker?

Something has to account for the pH crashes I've had while cycling with Bio Spira with a 2 dKH. It hits 0 in 1-2 days if I don't buffer.

This was the premise I was basing my advice on in helping Darwin. Any enlightenment would help, please ;)

Darwin,
I don't think happychem is saying that the advice I gave you to help you recover was bad, but rather my reasoning and cause/effect are faulty. Hope he clarifies!

Roan

[happychem]

Roan, the rate of buffer depletion is dependant on the rate of H+ production by the nitrifying colonies, which, in a cycled tank, is controlled by the rate of NH3 production.

In other words, if there are no established bacteria or no ammonia source, the buffer shouldn't deplete. In the case of an "accellerated" cycle you are effectively bringing the nitrifying colony from 0 to plenty, but the kinetic effect remains dependant on the ammonia source. In other words, if BioSpira were added and the fish were added the next day, or 12 hours later, then there should be no difference from a completed cycle in terms of H+ production and buffer consumption.

However, if the fish were in the tank for a few days producing ammonia prior to bacterial innoculation, then the abundance of food could result in a short lived pulse of H+ decreasing the buffer. However, this would not be indicative of a need for buffer addition in the cycled tank where bacterial H+ production is limited by NH3 production, which in general is not sufficiently fast to burn through the 35 ppm of buffer (a rough estimate of 2 degrees) in a week - assuming a proper stocking level.

Also, water utilities often buffer their treated water with polyphosphates to prevent corrosion in the lines and improve Cl2 life span. However, these would be consumed by plants and algae in the aquarium as a source of P. The result would be a baffling decrease in KH, because, of course, the aquarist assumes only carbonaceous species.

To come to the point, no, Roan, your advise was not wrong, per se. I was just trying to keep her life as simple as possible - the initial problem being too much monkeying with water chemistry.

The bottom line is that if your pH is crashing during your cycle, or during the week, and you are keeping up a proper weekly maintenance and not overstocking, then a little baking soda is the way to go.

As always, start from the advise here (which is usually fairly general) and modify to suit your settings. Otherwise you're not really learning aquatic husbandry, you're just following directions.

[Darwin]

Thanks for the follow up - I had been wondering about the consumption of carbonate. To begin with I thought it was only due to H+ produced during the nitrogen cycle but then I got the impression that it was due to actual consumption of carbonate by the bacteria (possibly a misunderstanding). That also got me wondering about whether some plants use carbonates as a carbon source.



If I had to guess, I'd say that the pH-Down killed or seriously distrupted your free floating fauna resulting in the bloom and the resulting O2 depletion killed your nitrifying colonies.


Just wondering what are the free floating fauna in the tank ?

When it happened I thought it might have been because the clown died. I found him in the morning and he looked like he'd been dead for awhile and the water was only slightly cloudy at that point. Perhaps if he was already decomposing that could have caused a bloom. When time I got home and the water was white the danios were gasping at the surface, so O2 depletion was probably the problem there. Otherwise, at the time i was doing very frequent water changes because of the sick clown.




Also, water utilities often buffer their treated water with polyphosphates to prevent corrosion in the lines and improve Cl2 life span. However, these would be consumed by plants and algae in the aquarium as a source of P. The result would be a baffling decrease in KH, because, of course, the aquarist assumes only carbonaceous species.


I don't quite understand this bit. Is it that polyphosphates can be an important source of buffering in tap water and that if these are depleted by plants, than you end up relying more on KH for buffering and might see more pronounced decreases in KH. In this case I would think that it be good to have a bit more carbonate buffering capacity. Or am I missing the point entirely ????

[Roan Art]

. . .Roan, the rate of buffer depletion is dependant on the rate of H+ production by the nitrifying colonies, which, in a cycled tank, is controlled by the rate of NH3 production. . . .

In other words, if there are no established bacteria or no ammonia source, the buffer shouldn't deplete. In the case of an "accellerated" cycle you are effectively bringing the nitrifying colony from 0 to plenty, but the kinetic effect remains dependant on the ammonia source. In other words, if BioSpira were added and the fish were added the next day, or 12 hours later, then there should be no difference from a completed cycle in terms of H+ production and buffer consumption.

However, if the fish were in the tank for a few days producing ammonia prior to bacterial innoculation, then the abundance of food could result in a short lived pulse of H+ decreasing the buffer. However, this would not be indicative of a need for buffer addition in the cycled tank where bacterial H+ production is limited by NH3 production, which in general is not sufficiently fast to burn through the 35 ppm of buffer (a rough estimate of 2 degrees) in a week - assuming a proper stocking level.What if the water contains 1.0 ppm NH4+? Along with regular stocking, of course, and added all at the same time at the very beginning with Bio Spira. Would that be sufficient to cause KH depletion?


Also, water utilities often buffer their treated water with polyphosphates to prevent corrosion in the lines and improve Cl2 life span. However, these would be consumed by plants and algae in the aquarium as a source of P. The result would be a baffling decrease in KH, because, of course, the aquarist assumes only carbonaceous species.Good point, and yes, mine is buffered with phosphates. However, and this is exactly what you are saying is wrong -- I WAS under the impression that plants consumed organic phosphates and not inorganic. At least, that's what I thought RTR was saying in a different thread. So, either I misunderstood RTR or I'm totally out in left field.

Can you explain further?


To come to the point, no, Roan, your advise was not wrong, per se. I was just trying to keep her life as simple as possible - the initial problem being too much monkeying with water chemistry.Noted ;)

Roan

[happychem]

Ooof! I'll try, but to be fair, I just moved and have been incommunicado for a while, so my head's really not in the game right now. ;)

Darwin, certainly the dead loach could have caused the bloom, I was just guessing at a timeline, but if the water was already cloudy it points to an existing disequilibrium in the free floating fauna. This is fairly common in newly established aquaria since you're starting from scratch, so everybody has to learn their place, if you catch my drift. Any perturbation during this initial equilibration time is going to prolong the bloom, evidently, it got much worse in this case.

You're not missing the point entirely, you're skirting it. The confusion here, I think, stems from the term KH, or carbonate hardness. Namely because that isn't what's being measured. What we're actually measuring is Alkalinity, the sum of all strong bases less the strong acid concentration. I've written an exhaustive description in the "Water Chemistry" article which can be found in "Article Corner". As a chemist, you might even understand some of it! :D Basically, both polyphosphates and carbonate species act as buffers. When you measure KH, you measure both; however, polyphosphates are consumed as a phosphorus source.

Yes, most plants and algae (at least marine algae), are capable of decarboxylation - using carbonate as a carbon source. However, the enzyme used to reduce the carbonate (Rubisco) is the slowest enzyme in the world, so this is not a favoured pathway for carbon uptake. Plants improve on this somewhat by saturating the enzyme with CO3, but it's still a slow process.

Plant uptake of CO2 is another possible route of carbonate removal, again, slow and I'm not convinced of its significance beyond theory. In theory when plants take up CO2 during the day, carbonate equilibrium will shift to replace the lost CO2. In theory this would increase pH and have no immediate effect on KH (because of the concommitant decrease in [H+]). However, the net result will be a decrease in [CO3--] and [HCO3-], leaving the system more vulnerable to H+ addition by bioacidification.

Roan, PO4 and polyphosphates are inorganic phosphate, this is analogus to CO2 being inorganic carbon. An example of organic phosphate might be a phospholipid or other compounds in which phosphorus was associated with carbon and hydrogen. As for whether plants will use organic PO4, I don't know. Probably they can, but there isn't a whole lot of it floating freely and using that which is built into their tissue would probably be a last resort.

[Darwin]

You're not missing the point entirely, you're skirting it. The confusion here, I think, stems from the term KH, or carbonate hardness. Namely because that isn't what's being measured. What we're actually measuring is Alkalinity, the sum of all strong bases less the strong acid concentration. I've written an exhaustive description in the "Water Chemistry" article which can be found in "Article Corner". As a chemist, you might even understand some of it! :D Basically, both polyphosphates and carbonate species act as buffers. When you measure KH, you measure both; however, polyphosphates are consumed as a phosphorus source.


I found your water chemistry article after my last post, it was a good chemistry refresher, thanks. Clearly I have been taking the 'carbonate' test way too literally ! From what I gather it seems fairly uncommon that people have tap water like mine, which is high pH (8 - 8.2) and low KH (2) and GH (2-3) or according to the water suppliers figures pH 7.8 - 8.7, KH 42 ppm and GH 47 ppm.