I went ahead and installed the jumbo sponge filters this weekend. Forgot about the buoyancy until they lose all the air! There's a weighted base but likely it would only hold one sponge down, and I had doubled them. Had a helluva time getting them to stay down. So when I first put the powerheads on they kept "hissing" because the cells were full of air. I squeezed them to get air out. I get one to stay down, then the other one floats up (across the tank).
So Pepper (rainbow) comes over and swims head on into the current, flying everywhere like a leaf. While he enjoyed himself twirling in the blast I tried anchoring the sponges on the opposite side. And of course, Brick had to investigate. I had just anchored everything in the sand, then Brick comes over and bangs his nose into the filter, sending it shooting up again like a floating log. He gets spooked, flies across the tank and I get a bath. Crazy ass O.
I ended up checking on the filters a couple more times but they stayed down. Love the water clarity. And with each rated for a 125 gal tank plus the hobs, water is ice clear.
Purchased a bag of pharmaceutical grade L-ascorbic vitamin C powder to dose the tank with, mostly for Brick. He's now stopped eating vitamin soaked mealworms. He'll only eat them 'crunchy'. I even tried drying them out after soaking but it doesn't work either. He also eats nightcrawlers but I found soaking them in vitamins makes their bodies go stringy and dissolve! So I'm determined to make sure he gets enough C. If I have to shake the powder over his head to get him to breathe /ingest it in, I will.