I've been using the filter that came with the tank (second hand stuff) since I got it a year ago, but my betta seems to have trouble with the current. He's found the dead spots in the tank where there is little to no current, so I kind of though all was well. Until yesterday when I finally found the sticker with the specs on it! It's 500L/hour and in a small 50L tank I asked in the store and they said 200L/hour for a 50L tank would be fine, but it depends on how many fish you have and what they are. Eventually I'd like to tank to have the two cories that are in there now, plus three guppies and maybe some neons if it doesn't overload the tank. Should I go for the 200L/hour or the next step up which is 380L/hour?