Water parameters questions

[gali]

I have a small 10 galon tank with 1 platy, 2 glowlight tetras, 2 lemon tetras. Decorations include regular aquarium gravel, plastic plants and a small castle aquarium decoration. Whisper 10 filter. It's been running for about 18 months with no special problems, although we lost a few fish at the begining (and a few more after we recently moved). We also have some green algae, although I scrape it off during water changes so it seems (more or less) under control.

It started as my son's tank, who at 3 was fascinated - although at this point he couldn't care less! I on the other hand got more interested, and got myself a birthday present a month ago - I'm setting up a 38 gallon tank .

While cycling the tank I only monitored Ammonia, Nitrite and Nitrate. This time I invested in a master kit. I tested my water and something seems wrong

Tap water - after stadning for 24 hours: pH ~7.4 GH 3 KH 3 Am 0.5 Ni 0 Na 0
Tank: pH > 8 GH 4 KH 4 Am 0 Ni 0 Na ~0.5

Today's pH reading was around 8.3, last week was around 8. I did one water change in between. I use Aquarium Pharm.'s tap water conditioner. Nothing else.

What's going on? This seems really weird to me. I intend to take a water sample to the lfs, to have them double check, but would like your opinion.

I also worry about stocking the new tank. The original plan was a peaceful community, but now it seems that I have alkaline soft water. It makes me wonder as almost everywhere I read that alkaline water is usually hard. Not mine! Anyone has similar conditions? I need some input about that as well.

Needless to say, I didn't know all that until now. I had a "mini pH" kit before, and everything seemed fine. Turns out the nice blue reading was simply the high end of the range it could measure - around 7.4, while the actual params were possible higher.

Any advice will be highly appreciated.

 

[benedictj]

I wouldn't catagorize your water as soft, but rather on the harder side of mid range (my interperation of soft is less than 4 degrees GH). Most test kits read KH and GH in german degrees, one degree equals 17.9 ppm (In case you didn't know, other wise just blow this off with a 'duh').

As far as the unstable pH is concerned, it is probably just disolved gasses giving you weird readings. Generally you won't get a reliable reading until 24 hours after you do a water change (once the gasses have disappated and the water has reached its equilibrium).

There are plenty of community fish which will tolerate your parameters, but if you would like to soften your water, simply add a healthy portion of plain peat moss to your filter and wait a bit.

 

[gali]

As far as the unstable pH is concerned, it is probably just disolved gasses giving you weird readings. Generally you won't get a reliable reading until 24 hours after you do a water change (once the gasses have disappated and the water has reached its equilibrium).

Actually, my concern is not about the difference between today's and last week's readings but rather about the difference betwen my tap wate (7.4) and that tank's (~8). Sorry if it wasn't clear.

 

[benedictj]

Oops. Well, what about your gravel and decorations? What have you got in there? It is possible that you have something in there which is leeching carbon, which will in turn drive up your pH.

 

[gali]

Carbon? How about the filter cartridge? Can that be it?
I only found out yesterday (here on the boards)! that cartridges are not necessary, so I intend to replace it with sponge/moss during the weekend anyway...

 

[benedictj]

Nope, different thing. What you are looking for is something that is forcing your KH levels up, activated carbon shouldn't do that.

If you compare the KH of your tap after 24 hours sit time to your tank it is higher which definitely shows something is leeching. Higher KH (carbonate hardness, the measure of carbonate ions) equals higher pH.

Do you have any limestone based rock in the tank? How about white, clacerous gravel?

 

[gali]

Do you have any limestone based rock in the tank? How about white, clacerous gravel?

No and no. I have regular gravel, probably plastic coated. black with some fluorecent pieces (it was selected by a 3 year old..)
other than that, plastic plants and an aquarium ornament - i don't think it's plastic but it's from the lps and supposed to be ok. we did have a lava stone there for a while, but it was supposed to inert. it was removed a little while ago.

 

[benedictj]

Black gravel can leech as well. Take a piece of it out of the tank, rub it well with some sandpaper and drop it in a small glass of vinegar. If it starts to form bubbles, then you have your culprit. (Not all gravels are created equal, plenty of companies sell 'aquarium safe' gravel which leeches.

Another remote option is a change in your water source. Are you on a public system?

And finally, one more option. How much evaporation occurs from the tank? When the evap happens, does it leave a white mineral film on the tank? If this is the case and you don't remove this stuff before adding water, it will disolve back in and increase your concentrations.

 

[RTR]

GH3/KH3 is soft water. GH4/KH4 is still soft water, but is 25% harder than the tap. To me that sound like evaporation with tap make-up water and insufficient water changes to dilute out the minerals left from evaporation, OR like a substrate with calcium carbonate in it.

What percentage water are you changeing and how frequently? Do have much evaporation between changes? If it is not that, then that leaves something in the tank and that is most often the substrate.

 

[gali]

GH3/KH3 is soft water. GH4/KH4 is still soft water, but is 25% harder than the tap.

Thanks for confirming that
I still need some recommendations for fish...

What percentage water are you changeing and how frequently? Do have much evaporation between changes? If it is not that, then that leaves something in the tank and that is most often the substrate.

I do about 25% every other week. There is definitely evaporation in between changes. I usually see some white residue before adding the water, so I guess this is it.
Will doing a weekly water change solve the problem? Any other tips?
It's especially important since I want to do things right with the new tank.