Problem with Aggressive Emperor Tetras and CO2

[davidru]

I am keeping a 30gal heavily planted Colombian Community tank. 3 weeks ago I switched from african rift-lake cichlids because they were too agressive and even though i got them to spawn and raised the fry they still killed themselves too much.

Now in the new setup I included 7 Emperor Tetras(5 males ~1.4 inches) and 7 other tetras that are very similar to Flag Tetras (~2 inches) and other fish. At the beggining the emperor tetras were shy but 1 and 1/2 weeks later they were comfortable. They started showing some agression towards the other tetras, but it wasn't that much. That week I brought more plants started inyecting CO2 to my plants and the PH dropped from 7 to about 6.2. From that day on all of the Emperor Tetras became much more aggressive and terrirorial, and the other tetras have to hide until about 5PM and some have their fins quite nipped already, though they recover quite fast. From 5PM on, the emperor tetras calm down and the other tetras can come out.

I suppose that the PH drop made the males get into a spawning mood, but is there any way to prevent this or how much time should it last? Is there any other effect from the C02 apart from the PH drop? The fish are not showing any symptoms of lacking Oxygen.

Do you have any experience with aggressive emperor tetras?

 

[TonyN]

6.2 is pretty low. I personally wouldn't keep it that low. You can raise it by adding baking soda. Start with 1/4 teaspoon and go from there.
A lot of people use crushed coral and swear that its the best way. A matter of opinion I guess.
If you decide to raise it, do it slow. No more than .2 or .3 in a 24 hour period.
Also be on the alert if your Co2 runs out. The pH will go thru the roof.

 

[aquariumfishguy]

I regret that I do not have time to fully read your post and answer everything here but I will say that Emperor Tetras actually like a more acidic pH. In fact, they would be fine all the way down to a pH of 5.5.

Changing the pH is much more stressful and hard on the fish than it is to just leave things where it is. Just keep fish that can handle a low pH.