I had an algae problem that was not quite as bad as yours but was headed that way. We do a weekly 75% water change and still have algae. I have a tendency to overfeed as well as leave the lights on longer for the plants. I believe both these contributed to my algae problem. Today my assistant cleaned that tank and all the decorations 3 TIMES, it took her several hours but the tank is sparkling clean. I highly recommend you do something like this immediately. It's easier if you remove the fish into several different buckets of tank water along with a bubbler to keep it oxygen in it. The scrub like there is no tomorrow. We changed all filters on the AquaClear except for the biobeads. The sponge (like yours probably is) was covered with vile amounts of sticky slimy brown stuff - it wasn't worth cleaning so we tossed it and the carbon filter out and put in fresh new ones.
Tonight I showed huge restraint and put in about 1/2 the food I usually do. My concern has always been that I have two night feeders in the tank and I always want food left over when I turn out the lights for them to eat. The dojos, I swear, eat 2x their body size, they must have stomachs as long as their 6 inch bodies and they are getting bigger all the time (I love these fish anyway) - they just don't know when to stop eating. They've always been my clean-up crew since they mostly eat pellets and any pellets left over in the morning after the night feeders eat seemed to be eaten by them. But they are sloppy and fast eaters. They crunch the pellets and excess particles fall out of their mouth and they don't want them.
I also bought a UV sterilizer a while back and used it on my 50 gallon tank, it seemed to help a little. This time we put it in the algae full - 29 gallon tank and we will see if it helps. But the three water changes and all that scrubbing at least got rid of all traces of algae in the tank (I'm sure some will come back). What IS frustrating is that both the dojos and the loaches I've got in there are supposed to love to eat algae - but I think they love the pellets much more because they show no interest in the algae in the tank.
This tank looks understocked but it isn't - it's jus that I have a quite a size assortment and one of the biggest eaters doesn't come out until the middle of the night: - 2 - 6" dojos, 2- 4" loaches and 12 tiny 1/2" neon tetras and 3 tiny 1" rasboras. It's kind of my "leftover" tank where I put fish where I'm overstocked elsewhere. Oh it also has a a 5" bristlenose pleco (female) that only eat at night. I rarely see her. I think our weekly heavy duty cleanings is the only thing that makes it not quite as bad as what you've had to deal with.
1. Make sure your tank is not over stocked
2. Change filter parts as directed by the manufacturer, instead of washing them in tank water and re-using them (once you've gotten rid of the algae problem that can change)
3. Make sure you are not over feeding - difficult to do if you have night eater but many of the night eaters also should be eating the algae.
4. Do a SERIOUS 75% water change multiple times and scrub every square inch of that tank, keep changing the water until it is clear - it may take 3-4 times in a row. Clean all plant leaves, remove all fake plants and clean them off and scrub off all the algae you can (we had some that just won't come off).
5, Continue from that point with weekly 75% water changes (hopefully only 1 of them per week).
6. Try a UV sterilizer (I'm on the fence about it myself).
7. Put your lights on a timer - perhaps 10 hours a day.
8. Check your filters every few hours to make sure they are not clogged up. - I have to "fix" mine several times a day due to plant debris.
Best of luck - you''ve got a lot of work in your future!
