sump media?

PoT Scrubbies or bio balls which ever is cheapest in your area, ceramic rings are a good choice also really its what you want to use and can afford to buy depending on how big a sump you have.

^ no no no no no

Do NOT put bioballs in your sump unless you like taking them all out to rinse them off once a week.. (defeating the purpose of bio balls.

Do some searching on bioballs and such in salt tanks... The best combo that I've found is to build a DSB with live rock and lots of macro... That plus skimming is probably the best thing to remove excess nutrients/waste from your system.

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

No it won't lead to blooms in your main tank if you do it right. It leads to the exact opposite. Search it on here I think (or try google) theres a huge FAQ on them somewhere with some really good descriptions, links, ideas, and the experience of a LOT of people who have used them. It's the 100% definitive algae scrubber thread

Yeah! Search "Algae Turf Scrubber" Read the thread by Santamonica -Most powerful Nitrate remover, or something like that. VERY exciting. I'm getting all the parts to build one too!