08-01-2011, 09:32 AM
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Some surface movement is fine; you will find very knowledgeable planted tank authors saying it is irrelevant, others think it matters. I think the best approach is not to overdo it.
Most fish do not like water currents that are excessive, and HOB filters in my experience tend to have more water flow than canister or sponge filters. Unless you have fish that need water movement, such as some catfish, hillstream loaches, and others. Otherwise, minimal flow is best for the fish, and then you needn't worry about gassing out the CO2.
Clubber, water seems fine for Valls. I doubt it is the swordtails. Hard water is mainly calcium and magnesium, so other nutrients may be lacking; Flourish Comp twice weekly (if once weekly now) might help.