If you are not going to depend on filtration and bacterial action consider sodium carbonate peroxyhydrate which is an addition compound of sodium carbonate and hydrogen peroxide (H2O2) an oxidizer. At lower concentrations is not toxic to fish and works well on inactivating bacteria and most algae. The nominal amount of sodium carbonate peroxyhydrate is 85% in PAK®27 which corresponds to 27.6% H2O2. If you are interested, I can check on the feasible rate of application.
