here my input on this one...i do 90% water changes two times a week (i would do 100% but some fish are thriveing with the turts) i when i do water changes i soak my bio media in the tank as the water goes down and when i fill i let the ne fresh water run over it once the tank is filled then i put the media back to appropriate filters...most turts like calmer waters so to strong of a current may discourage them from the swimming, if you feel the current is to strong redecorate your tank with obsticales (small part of basking platform, fake plants, rocks?, what ever you want) so the filter waterfalls into the obstacles and becomes more like drops hitting the water rather then a small stream flowing into the tank...the drops will break the surface of the water but their will be minimum to no current in the actual body of water...sorry if any of this was already stated i didnt feel like reading the two pages...hope that helps