Sounds like you guys dont have a solid nitrogen cycle! I strongly suggest getting a testing kit (a decent and cheap one would be an API fw liquid test kit), test for ammonia, nitrites, and nitrates daily. I'd do 50% water changes daily and add in prime, do not replace your filtration as that's nerfing your biological cycle! Use aquarium sponge filters Like this and filterfloss for the small stuff like this. You want 0 ammonia, 0 nitrite, and up to 40ppm nitrates. The algae is from unstable water perams.