Even with an airstone, which I wouldn't use, but won't get into it, the water the airstone provided oxygen for must be moved around the whole tank, and airstones don't do that very well. "skimmers remove algae".....not really, and not dead algae either....cyano is bacteria anyway, and skimmers don't remove algae, bacteria, or the nitrates released after algae dies. They only remove things thjat are attracted to the surface between air and water. Try to fix this without chemicals in my opinion....it will be a learning experience, and it won't be that hard to do.