Thanks Doc, for addressing this common problem that the OP & I are having.
Each tank is 10g w/ Penguin 100 HOB + sponge filter. One tank is in a dark room inside the TV section of an entertainment console. Never in direct sunlight. Other tank receives indirect sunlight from an adjacent window. Both tanks are equally green/yellow but "clear". Tanks lights are nearly never on. Both are planted with bunches of java fern and anubias, which are both doing well. Ordinary (non-fluorite) gravel for both, too.
Water changes are 20% 2x/week.
Any build up in filter or tank?
No algae build-up in tank & filter is rinsed in aquarium water ~ q10 days.
How old is the tank?
About 7 mos. (1 bought new, the other had been out of service for about 2 years)
Have you made changes recently?
Nope. Everything is "as is" from the start.
Stocking levels?
1 male betta + 2 peppered corys in one tank, 1 male betta + 3 black neon tetras in the other.
Possible over-feeding?
Doubtful as each betta gets ~6 pellets per day. Corys get sinking microwafers or discs. Tetras get sinking microwafers and avg. 4-6 "bites" per fish. Yes, I really do sit there and watch/count.
Anything you've already tried?
Other than upping my water changes, I've tried a round of "Al-gone" . I thought is was working, but no dice.
Can you borrow or buy a UV sterilyzer?
That was going to be my next step. I was going to rig a UV steri. to an old HOT Magnum filled with media, carbon and filter floss in an effort to polish and sterilize. I was planning on rotating the Magnum to each of my tanks for 2-3 days each.
IDK.... at least the fish are healthy!
Regards,
-cd