I have several acrylic tanks that have been long established! The three larger ones (20, 30 & 40 gallon have no algae issues at all. All 5 of my 5 gallon male betta tanks (planted) have brown algae on the tank walls that simply will not go away! I scrub on small spot till my wrist is about to fall off and it STILL won't budge! The snails will not touch it! The bettas get fed pellets once a day; there is virtually no fish waste; no decaying plants; Filter media is changed every 2-3 weeks; Have to have a slow current or the bettas get exhausted form fighting the higher flow rate; what can I do? I am using city water (RO water is so prohibitively expensive and it takes ages with one of those small "spouts" connected to the RO source under the sink, it would take HOURS to do a water change on those tanks. I don't think it can be the water source as there is no problem with the larger tanks.
I am at a total loss here!
