I put 15 snails and 20 blue hermit crabs in my 90 gallon. If you have been or do some water changes, I would think you would remove or seriously dilute the silicates. To you have a TDS meter? I got one with my RO/DI system. Mine reads 1 on my RO water and about 60 on my tap water. You can't really hook the filter up wrong and get any water out. I'm pretty sure any water you are putting in has no silicates. If you are doing small (5% or so) water changes, try to do a couple larger ones. One 20% change will get out more toxins than four 5% changes. It probably took me a couple months to get rid of the hair algae. I also knocked if off and let it get into a filter pad somewhere and then cleaned the filter out. I have my canister setup so that I can move the intake around the tank and "vacuum" the tank. Then I clean out the sponge in the canister. I have also been using a product called Algone and one called Purigen. I don't think the Algone has done much for me. The Purigen I just started and it seems to be doing a little. I think the biggest was the snails, then the RO water, then the crabs. I don't think the addition of some more snails could hurt a tank. I would try that and some water changes, give it a month and see what happens. I would also say that I have never heard any one else talk about silicates. I have heard nitrates and phosphates. Maybe your area is know for having certain things in the tap water. RO never hurts and water changes never hurt. I would say 25% change as a max at one time. I have heard people say 50%, but I wouldn't do it. I would do 25% than wait about 3 days and do another 25%. Remember these are my opinions. Everyone has there own. I've only been doing this for about 8 months. I'm learning a lot also. Many people have these filters and many people have ways to help reduce algae. You might want to search some other threads and even post a thread that doesn't address me. Not that I don't want to help, because I do. Others that might have good suggestions for you, might not read this thread since it is addressed to me. And remember you will always have to weed through some bad ideas when you get many suggestions.