In response to a problem with ammonia that I've been having, I got a new Penguin filter with a bio-wheel. It's rated for 30 gallons, and is being used in my 20 gallon. I took out the Aqueon filter, since I don't really see how bacteria are supposed to survive when you change the filter. It survives on the biowheel and filter media. You are not supposed to take out the cartridges unless there is a biowheel or something else with the beneficial bacteria. If you take out the cartridge and that is all the filter media in your filter, you will end up with a mini, or full cycle. Clean the cartridge with old tank water and re-use it. Or, shove a new cartridge/filter media in there along with the old cartridge, then you can take out the old one and the new one will have at least some bacteria colony on it.
Anyway, my platies are spending a lot of time swimming in the current, which is stronger than before. The other fish don't seem bothered by it, and there are plenty of spaces that are current-free. But in your experience, do fish typically like currents? Are there any that are adverse to it?
I've asked this same question. Not totally sure of the answer, but research where the fish comes from - if their origin has currents, or no currents, that will help you find your answer....