How much rock for proper filtration?

[G_Lows]

I’m considering converting my 80gal rimless to a frag tank. I would like to run racks only in the display with virtually no rock. I have a triton 34 sump and would use the fuge section to pack with live rock that I’ve had for about 2 years. Would that be enough rock to sustain the system?

 

[ichthyogeek]

Potentially yes, but it's dependent on what type of live rock you have. Remember that a lower mass:volume rock allows for a larger surface area:volume ratio, and that dense rock = less holes for bacteria to colonize. So Pukani rock would be amazing, while sheet rock would not.

I also think you'd eventually run into detritus issues in the lower layers of rock. This can be remedied by turkey basting the rock regularly, and regularly removing detritus from the bottom layers. Oh, and that only the top layers of rock may be oxygenated enough to allow for nitrification, unless you utilize a way of water flow that flows through the bottom and pushes water up. Finally, don't "pack" the live rock together too much; a little is fine, but if it's all stacked up neatly, then bacteria will have less places to thrive.

Maybe consider using sponges, bioblocks, or other forms of nitrifying media. Those may be superior to other, denser rocks (ex. Texas Holey Rock).

 

[Billdogg]

In addition to what ichthyogeek said, remember that as a frag tank it will have a relatively low bioload, so you can probably get away with less than you think.

That being said, I use a 100g rubbermaid stock tank as the sump for my 60g FT. I keep it pretty full of LR with none in the FT, but like to switch things around from tank to tank so it gets moved around often. I find it especially helpful when setting up my QT. I have plenty of well established LR on hand so I can just grab a chunk or three, put them in the QT, fill it up with water from the FT and go with it.