| | Re: How much water flow is enough
More water surface the better - as long as, like the other member wrote, the fish don't have to use surfboards - because it provides more oxygen in the water column. Water surface agitation: the bubbles that bounce all over the water surface exchanges with the air oxygen above the water surface which turns into a gas exchange which when the bubbles burst at hundreds of times per minute creates the oxygen in the water column.
Also agitation or a flow in the water column is good for most freshwater fish for they prefer movement like in nature, streams/rivers where most freshwater fish originate from, it is in their instincts to have a current - like in my tank, in one corner, there is a bubble disk with 2 air stones which create hundreds of bubbles which create the movement in the water column plus the fish, most of the time, will literally go nose down against the upcoming bubbles as if the fish will swimming against a current, it's fascinating to watch plus I assume it is good exercise for them, for I'm sure the fish do not realize it is just air stones and a bubble disk, but in their heads or in their nature, it appears to them that the water is racing up against them and they are "traveling" against the current or stream/river.
So my advice is, either get a spray bar, water flow pump, hang over back (of the tank) so the outlets help produce the current and/or bubble disks or air stones (or a mixture of these devices) to create the much required water surface agitation and/or stream-like effect for the fish.
My only other advice is, there should be some dead spots in the tank, that is, where the water is absolutely still for some freshwater fish prefer no current. That way, you please all the fish in the tank.