I have a huma and pocupine puffer in a 100 fowlr. Both are a good size. Before transferring them into that tank, I had a clean up crew of about 60 hermits, a mix of blue legs and red legs, 4 queen conches, 4 turbos and 10 nassarius snails. I took a gamble and all were gone within a couple of months. Since then, only a handful of the larger red legs survived. They don't roam the tank like they used to during the day, but at night they do come out. All I could recommend would be water changes with RO water, scrubbing pads, a magfloat, and a scraper. You could re-stock the tank occassionally but that would only provide temporary help.