media volume vs. water volume - w/d biofilter

[Sploke]

For the filter on my 150 I used DIY plans from cichlid forum to build a nice wet/dry system, with a 3-drawer sterilite cart. 2 of the drawers are filled with lava rock as biomedia. I would like to use a similar system when I set up a central sump. Just wondering if there are any guidelines as to how much volume of biomedia you need for a given tank volume? I know my 150 is probably overfiltered, it runs about 3x per hour turnover wit a fair amount of media...how much should I use to filter roughly 500gal at 2-3x per hour?

[Nolapete]

I would start by looking at the commercially available wet/dry systems and see how much media they hold, what type, and what size tank they are rated for. Then look at the media and see what the surface area is compared to the surface area of lava rock. (I'd suggest using something other than lava rock since lava rock is going to hold a lot of organic debris)

[mostlycichlids]

Matt, certain types of media have more or less surface area. Therefore there is really no set number in regards to filter media to water volume. I would go with ceramic cylindars, or bio balls as they have the most surface area. This being said you would need less media opposed to if you were using sponges or pot scrubbers. The more the better I guess but you may want to play around with it a little. Do a search on bio media surface area. There are graphs that show the different surface areas and compare different media.