Stupid 5-gal Hex

[candycane]

Today I decided to put the filter back into my 5-gal hex. Then I remembered that last time I had the filter in it, the pH went from 7.2 to 8.something. Is it because it is adding too much oxygen to the water causing the pH to rise? Can I prevent this from happening somehow?

[mdellasalla]

Some filters do cause the pH to rise in the water, but it is more because too much oxygen is added to the water replacing much of the necessary CO2. The CO2 acts as a buffering agent between the carbon released in your plant and fish waste and the converted carbonic acid created by bacteria. Without the CO2, the levels of carbonic acid rise, and with too little CO2 you will have an overabundance of bicarbonate salts.

If you have noticed your filter doing this before, then I don't think you would be able to change the way your filter works and getting another one doesn't seem like a good idea because you don't know what will happen to that one. I would suggest getting a pH down buffer kit or not using the filter. Since your tank is bigger you might want to just go with the pH buffer. You are going to have to monitor the pH closely though to make sure it stays where it should be. I know my brother had this problem with his 30 gal tank and he was always fighting the pH. (He also had problems with the fish that he put in there though, it wasn't solely the filter )

[bettalvr]

Just remember to be very careful with any pH down. . . it's acid! Drop your pH VERY slowly over the course of a few days.

Another alternative is to add the Indian Almond Leaves or IAL spa. This lowers pH also.