Wild pH Swings


My name is Michael Livingston, and I have just joined the list.  I have tried to grow aquatic plants on and off for many years with little success.  Well, I am in an "on" cycle now and through this list and other 'Net sources I think I will have much more success.  Right now I have a 15 gallon tank, a Fluval 303 filter (yes, it is plenty powerful), a Coralife 6500k 15w reflector bulb and as many plants as I can find. Right now they are Cabomba, Hygrophilia Difformis, Amazon Swords, Water Millfolia and a few others I am not sure about.  I have a few algae eating fish, a Flying Fox and two plecos (very small), as well as a few neons and White Clouds I just can't flush.  I am feeding them only sparingly and every other day to keep wastes down till the tank cycles which seems to be going OK.  My Wardley test kits say only trace Ammonia after one and one half weeks, no nitrite and no nitrate.

I am using a DIY CO2 injection system (if "system" is the word).  The gas bubbles out of an airstone and is trapped at the surface in a small inverted plastic container.  Once I started using this system the pH values dropped from around 7.2 that night to 6.2 by morning!!??!!  It was back around 7.0 when I got home from work.  I pulled the airstone out overnight and the pH slid up to 7.2 the next morning.  This has been going on for a couple of days now and I am sure that changes like this can't be good for the plants or the fish.

After all that, what can I do to minimize these changes.  I have read that kH (or is it alkalinity per recent flames :) ), pH and CO2 are tied together.  My water has a kH of 4 per the Tetra tests.  Will raising the kH help stabalize the pH?  Can I use aquarium salt or baking soda to bring the kH up?  Are there other better suggestions?

Thanks In Advance!


P.S. Is there a non-digest version of this list?  If so how may I switch?