Just to add my 2 cents worth. I work in a pet store, which has a 75 gallon reef that has been set up for 15 years. For most of the time, it has been run on powerheads, and a protien skimmer. 8 monthe ago we decided to put ecosystem's miracle mud sump on the system. The first month was a little crazy with a 24 hr light source, lots of cyano, but after the system settled in, it really has worked wonders. Our water is crystal clear, corals are opening up larger than ever before. The only coral that wasn't was a finger leather that was sandwiched between a hammer and a pearl, once we gave it a little more room, it started thriving as well. The reason you don't need a skimmer is that as the calerpa grows, just like plants, it uses up the organic wastes that the fish are producing. There is only one species of calurpa that has been prohibited, because it is not a naturally occuring species on this coast, it origionated off the coast of austrailia, and was transported here by aquariums, with no natural predator, has taken over a lot of area, but if you stay away from that one, you will be fine. I can't find the article that lists it's name specifically, but it looks just like a feather, stay with the flat stranded kind, or the grape stuff and you'll do fine. We were also a little cynical about it's clame to improve fish health, we had a customer who brought in a
red sea sailfin tang that was just about eaten away with HLLE, and after 2 weeks in our 75, there is almost no trace of it on him. I attribute that to the system, just regular healing, and removing him from the environment he was in would have taken much longer than 2 weeks. I think it's kind of funny that someone can claim to know what a substance is made of by looking at it under a microscope, much like trying to decipher what is on a cd by looking at the grooves. After 8 months of doing nothing but adding water for evaporation (we don't even feed anymore, with all the organisms growing in the sump), nitrates have leveled off at 2ppm. In the tank are the red sea sailfin, royal gramma, mandarin (which has been in there for 7 months, and a flame angel. I would say this stuff works. I'm sure there ae other systems that work just as well, but htis is totally hands off, and we haven't had any problems at all. The mud may be a bit pricey, but so is the entire hobby.