Hi there is my first post here and I have become very interested in bimacs. I have read most of the articles thus far. One thing that I have a question on is filtration. I assume LR is better than a wet/dry. What do you guys use for filtration? Would a wet/dry filter, a hang on tank refugium, plus about 30 LBS of LR be good for a bimac in a 75 gallon tank?

Well, there are different schools of thought on that one...personally, I prefer to use live rock and a lot of physical filteration over a wet/dry, but that is also due to the fact that I live in the desert, and evaporation takes too heavy of a toll on the refugium.

I think your setup WITH a wet/dry sounds good.

Many reef enthusiasts believe that removal of the bio balls is beneficial to filtrations as it produced less nitrates. I disagree, most wet/drys have bio balls in the dry section, but not in the wet where denitrification happens. If all your media is in the ammonia processing area (which EVERYONE agrees does a great job), there isn't any media for denitrification and you get nitrates. I put equal amounts of bio balls in the top and bottom of my DIY wet/dry and just did a long messy cycle with multiple bumps and my nitrate is at 10 ppm and dropping. :grin:

Ask 10 people and you will get 11 answers (...and my brother did it this way.) Whatever you do- be prepared to handle nitrates through denitrification or water changes. In my opinion -live rock takes a long time to meet its potential for nitrates, and that ceiling still has less surface area than bio balls.

Would a refugium take care of nitrates?

Depends on whats in there. You could use it to grow macroalgae which can help with denitrification quite a lot. I've also know people use mangrove trees in there for that reason as well though I don't know how well this method works.

Would a refugium take care of nitrates?

If you stack it full of Cheato or mangrove it would. You then have to trim back the algae growth, it's called "nutrient export".