If you must use an alternate form of filtration look up algae scrubbers
Also, you can use carbon to help clear up water and to do some absorbtion.
Some type of phosphorus removal device is another good chemical filter to have
And finally some people swear by purigen and other types of chemical media... The general rule though is that biological filtration should happen with live rock, sand, and macro. Mechanical by your skimmer and maybe an easy to clean pot scrubber, and chemical varies by bioload, water, etc