Raising pH or buffering pH??

[Galerius]

Hi,
My tap water straight from the faucet reads between a 7.5 to 7.8, with a general hardness of 30-35 ppm. My 45 gallon FW tank (with misc. tetras, loaches, and previously, angelfish) generally reads about a 6.0 or less before water changes. After bi-weekly 20% water changes, my pH reads about a 6.6-6.7, perfect for my fish, but in 2 weeks, it crashed again. I know that the pH swing has to be caused by a lack of natural buffers in the water, but other than chemicals, what natural way can I raise/stabilize the pH, without stressing out my fish? Also, I've read/heard that nitrification bacteria stops functioning properly below pH 6.0. My eventual goal is to upgrade to a 90 or 125 gallon tank for discus, but I'd like to solve this riddle first.

My current tank set up is this: 45 gal FW, Fluval 404 canister w/ Bio-wheel 60 attached, temp is 80 degrees F, double 48" standard flourescent lighting, moderately planted (java fern loves neglect) with no additional plant nutrients added or CO2. Current residents: 4 overgrown bleeding heart tetras, 6 lamp eye tetras, and 3 clown loaches (the oldest is 3.5 inches long, the middle is 5 inches long, and the youngest is about 8 inches long). The tank has been established for 6 years, and the pH swing problem began after my latest yearly 80% water change and major gravel cleaning.

 

[Biggen]

After bi-weekly 20% water changes, my pH reads about a 6.6-6.7, perfect for my fish, but in 2 weeks, it crashed again. I know that the pH swing has to be caused by a lack of natural buffers in the water, but other than chemicals, what natural way can I raise/stabilize the pH, without stressing out my fish?

. This simply means that you need to change your water weekly instead of bi-weekly. Your fish will love you for it.

You can raise the KH level of your tank by adding in Baking Soda (Sodium Bicarbonate). You could start with a teaspoon or two and day and work your way up to your desired pH.

You could also add coral/shells to the tank, but this will increase the GH value as well as the KH value. However, since it uncontrolled, you will have to monitor the values all the time.

I still think your best bet is to simply do weekly water changes. I do it and never seem to have a problem with pH swings.

Also, I've read/heard that nitrification bacteria stops functioning properly below pH 6.0.

Correct. Ideal conditions for nitrifying bacteria is a pH of 7.5 - 8.5 but they will adapt out of that range. Anything below 6.0, however, will slow them down tremendously.