freshwater tanks ph level

Question
Hi.  I am a new freshwater fish enthusiast and I am having problems keeping
my ph at a safe and normal level.  No matter how many times I adjust the
level it always returns to 6.0.  I have 4 glofish.  One seems to be affected by
the level.  When it is above 6.0 it is full of life like the others until the ph
drops back down to 6.0.  Then it is lethargic again.  How can I keep the ph at
a normal level?  So far I have changed 20percent of the water and still no
change.  Please help.  I dont want to loose any fish!

Answer
Hi Jennifer
Well, 6.0 is still within a "normal" range of what most fish can tolerate.  What's happening when you add the chemical to adjust the ph(and I'm assuming you're using something like PH UP), there's obviously no buffer/hardness so the ph just drops back down, and quickly.  This will definitely stress and even kill the fish.  

First what you should do, is check your tap water ph.  Get a glass of water and do a ph test on it to see what it is.  Then let it sit out for about 12 hours and retest it.  That should be about what's going on in your tank.  

If the ph in your tank is lower then what your test results were, then something in your tank is causing it to crash.  Possibilities could be driftwood, not enough water changes-too much waste build up(should be doing 25% weekly for most tanks), not enough aeration/CO2 build up in the water.

I usually don't advise people to mess with the ph, but if your fish is acting stressed from the low ph and not from it lowering too quickly at one time, there's a few options.  You could try increasing the aeration in the tank to drive off the CO2 and add more O2 in the water.  An air stone would work, but the thing with increasing the O2, there needs to be surface agitation-that's how the gases exchange at the surface.  A lot of people think that just putting an air stone in adds oxygen, but if it's too low in the tank and isn't agitating the surface, it's not doing anything.  Or, you could make sure the water level is down about 1/2-1 inch from the waterfall output of the filter.  That's usually more then adequate for allowing the gases to exchange.

Another option, adding limestone rocks to the tank or crushed coral-anything that contains calcium carbonate.  To check rocks that would work, pour some white vinegar on them.  If they bubble or foam, they contain calcium carbonate and will raise the ph in the tank.

Another option is to use RO water. But, depending on your tank size, that may not be feasible or easy.  You would also need to be an additive to add the minerals and such back into the water since those are removed during the RO process.

What you need to watch though, when you alter your ph in the tank, it'll be different then the water you add when you do your water changes. And, that can be enough to cause ph shock in the fish when the ph alters when you add the new water.  So, you need to devise a way to increase the ph in your new water before adding to the tank.  Some people have large bins or containers and treat the water days before adding it through various means.  You could probably get away with adding a liquid or powder ph up product to the new water, and the tank water should have a high enough gh/kh to "hold" that ph level in the new water.  It's kind of difficult to explain really, but here's a few articles I have saved.  Kind of boring reads :)  But interesting none the less.  But there is more involved to it then just adding some chemicals in.

http://www.chelonia.org/Articles/waterchemistry.htm

http://aquaticconcepts.thekrib.com/Articles/Water_Chemistry.htm

Hope that helps and let me know if you have more questions.

Christy