Why is PH changing?

[Hootchieman]

I have a 72 gallon planted tank. Over the last few weeks the PH has dropped from about 7.0 to 6.0 - more acidic. All of the parameters ammonia, ites, ates are fine and I do a 30% water change every week but the PH keeps dropping. I have added some Flourish to the tank for the plants but don't know if it could cause a PH change. My 10 gallon tank has maintained a constant PH of about 7.2 and it gets the same treatment. Any ideas?

:confused:

[slipknottin]

did you test Ph the same time of the day?

[MP]

What is KH of your tap water?

[slipknottin]

MP- you got a PM :)

[Hootchieman]

I have tested the large tank in the evening as well as during the day with the same results. The water hardness is medium-soft. Sorry I don't have a number for you on hardness but I will test it again. I don't know if the change is due to all of the rain we have had lately. I will check the tap water directly tonight. I just don't know what is different between my 10 gallon and 72. Thanks for the suggestions.

[slipknottin]

try testing the Ph in the morning before the lights come on.


have the plants started growing alot faster after you added the fluorish?

[wetmanNY]

Hootchieman, you mention recent rains affecting your water-- if you're catching rainwater in a cistern I really envy you. In twenty years even the U.S. will be doing it.

The rainwater is even softer than your usual water. It dilutes the buffer, making your pH more flexible...

...but it doesn't drive the pH down very much, though the pH of rainwater is generally around 5.7. By contrast, the CO2 respired by fish and plankton etc is a major force depressing the pH. CO2 is also produced when plant and food detritus naturally degrades."Bio-acidification."

Three ways to counter this natural "bioacidification:"

1.Photosynthesis uses CO2 and raises unbuffered pH, so increase the lights (don't add more fertilizer).

2.Flush out your filter more often. (You probably have canisters, eh.)

3.Vacuum up all plant debris off the surface of your substrate. (don't disturb it though)

[Hootchieman]

Yes Slip the Flourish is working. My Cabomba seems to grow an inch each day. I am worried that if the water gets too acidic that the plants will start to rot.

Wetman, I have a Millenium 2000 hang on filter as well as a Fluval 404. I just cleaned both filters last night and yes they were pretty plugged. I will check PH tonight again to see if things have changed.

Thanks for the input.

[slipknottin]

yup... this is definatly a water problem outside of your tank.

if your plants are growing well and the Ph is still falling you need to look at your source of water. you could add a small bag of crushed coral to your filter to maintain the Ph.

[wetmanNY]

hmm. stumped. ...but they were such sensible ideas...

Your pH indicator is methylene blue surely. Very stable. I don't think it goes out of date. Am I right on this assumption, gang?

[Rocketman]

Hey, what do you mean you use rainwater? In the US, isn't it illegal to use any naturally faling water for anything that may bring it in contact with and wildlife...?

Anyway, make sure you wait a good 24 hours before you test your tap water for pH, this gives the chemicals time to dissapate...who knows some of our acid rain may have fallen across your border?

[slipknottin]

Originally posted by Rocketman
Hey, what do you mean you use rainwater? In the US, isn't it illegal to use any naturally faling water for anything that may bring it in contact with and wildlife...?



ive never heard that... whats the reason? dont fish that live in ponds and lakes get rain water too? :confused:

[perrito_blanco]

I had a similar problem in the past and solved it (with the help of a few great forum members) by adding baking soda to the water to keep the KH around 2-3 ppm. This is something that I have to keep an eye on. I test weekly. Lots of fish were dying... it was a terrible scene.

Don't let this happen to you! The fish are being stressed out big time!

Keep an eye on the KH.

[OrionGirl]

Rocketman--not sure if this is what you're thinking, but there are in fact laws regarding the use of water that is in streams/rivers/lakes. You can't just take the water out of a flowing system and use it for whatever you want, nor can you return water to a system without certain permits.

Most states have instream flow legislation that determines who can take what amount of water from each system, as well as what it can be used for, and if it can be returned to the system. None of these laws limit the private collection of rain water for personal use (watering, drink, fish tanks, etc). Release of this water may be limited, depending on use and your location.

[wetmanNY]

perrito, the baking soda you used was "bicarbonate of soda" I think sodium bicarbonate doesn't stabilize pH like calcium carbonate does.

nah, Rocketman, those British Columbians get their weather fresh from the Pacific! There's more than a whiff of algally-produced sulfur in those damp seabreezes though. I think* it's carried as dimethyl sulfide. The sulfide gets oxidized to sulfate (SO4) in the atmosphere, and then when oceanic rain hits the unbuffered watershed, it does put some H2SO4 and maybe even some acrylic acid into the percolation. Voila! naturally-produced polluted acid rain! This is at issue in Scandinavia, with oceanic sulfur raining into granitic lakes.

Now I shall refresh myself with a www.google.com search: what was it? ah dimethyl sulfide . Bound to be geekatoid links in that one!

*think? hah! I just checked James Lovelock, The Ages of Gaia: a biography of our living earth and got the name of this chemical, which wastn't exactlyon the tip of my tongue, eh.

Yes! very satisfying geekatoid links!

[Rocketman]

I was being a little sarcastic with the illigal rainwater bit, but what I was trying to say is that the rainwater we get here is straight from the most polluted place on earth - Gary, Indiana. So, using this reasoning, I figured anyone in Michigan could most likely be sued by some animal rights group for making such a dumb mistake of killing their fish instantly with Michigan Rainwater. Hell, it could probably kill a person. I once had to test the Rogue River as part of this annual clean-up deal...community service...
The test results were skilled on a chart - "Safe for human drinking water...safe for human swimming...safe for filtered drinking water and bathing... safe for vertabre life forms... safe for invertabre life forms...safe for protozoan life forms...unsafe for any life form..."
Needless to say, the tests came back negative for the first one... and the second one... and barely made it to the filtered water result. Still, there was E. Coli crawling all over our petri dish sample.

[perrito_blanco]

Originally posted by wetmanNY
[B]perrito, the baking soda you used was "bicarbonate of soda" I think sodium bicarbonate doesn't stabilize pH like calcium carbonate does.

Calcium carbonate will also raise his GH though. We don't know what his levels are of either.


I was being a little sarcastic with the illigal rainwater bit, but what I was trying to say is that the rainwater we get here is straight from the most polluted place on earth - Gary, Indiana.
Would running it though a canister filter with mucho activated carbon make it safe for use?

[wetmanNY]

Sure it'll raise the totals of Hootchieman's "general hardness" which includes the "carbonate" hardness responsible for the KH reading, plus all other dissolved salts. Hootchieman was posting for explanations of the falling pH (from 7.0 to 6.0) in his medium-soft water. Perritobianco's experience with sodium bicarbonate (HNaCO3) reminds us that it doesn't stabilize pH, though it does temporarily boost it. When the CO2 dissociates, you're left with that Na that doesn't work as a buffer.

Perrito's got a good point about filtering rainwater with activated carbon. I'd add floss too, for particulates. I'd even use PolyFilter.

But of course by the time rain hits a swamp it's swampwater, or riverwater-- or in my case it would be tarpaper roofwater. That's not not nice either!

[perrito_blanco]

Originally posted by wetmanNY
Sure it'll raise the totals of Hootchieman's "general hardness" which includes the "carbonate" hardness responsible for the KH reading, plus all other dissolved salts. Hootchieman was posting for explanations of the falling pH (from 7.0 to 6.0) in his medium-soft water. Perritobianco's experience with sodium bicarbonate (HNaCO3) reminds us that it doesn't stabilize pH, though it does temporarily boost it. When the CO2 dissociates, you're left with that Na that doesn't work as a buffer.

OK. So your saying calcium carbonate will stabilize the pH with the initial application? If so, sounds good. Where could I pickup some?

[DGC]

nearly 10 years ago, in your opinion how would you answer this interested to see

[prober]

Ha ha, a little post mining. Interesting topic, you struck gold on this one.

Without getting into the physics and chemistry of tar paper roof water, there are a couple clues here. I think it may be a combination of a couple things. First, he started dosing ferts making his plants accelerate which could have caused a lowering of the KH making the PH less stable. Also the rainwater being added could be lowering the PH although he states that his smaller tank gets the same treatment and is still stable. Assuming that he is changing water at the same percentage and frequency in both tanks would tend to rule out the rain water. That really just leaves the increased plant activity. Lastly, his filters being plugged could have added to the problem with reduced filtration/circulation and the acidic by-products of decaying matter in the filters.

Then again I could have completely missed something obvious but it was a fun exercise anyway.

And my answer for how to treat his water would be to use alkaline and acid buffers to raise the GH and KH while targeting a specific PH. A much better answer than just using shells or baking soda since it can be measured and provide specific results.

[DGC]

nice answer, difference with this is i dont know if any of the guys are still here so we cant ask questions - theory only enjoy.