Originally Posted by MSG
I go with larger than necessary because it reduces the amount of WC for me......
For example I have a filter rated for.....
30G in a 6Gallon + new 10G filter for testing
40G in a 10G
80G in a 30G
I haven't done any water changes in at least 2 weeks now. Ammonia is still 0.
You can go with a smaller filter, but you'll have to do some extra water changes to lower the toxics because the filter won't be able to keep up.
that doesn't sound particularly safe for bettas....an unnecessarily strong filter in too little water can lead to even more risk of fin catching/tearing, especially for breeds like VT's and HM's which have very long fins.