[Mr.Lizard]

Oh- and Oldmill- I am currently running a 55g reef without a skimmer, and I seldom do much more than add water for evaporation make up. I think Wildthing has it right, though- you really need to make up used trace elements and such somehow, and replacing some of the water with a good salt mix is an easy way to do it....I also add some with B-Ionic and SeaChem Trace, especially since I have a bunch of corals, fish, one derasa, and one gold maxima. I also use the Boyd's Chemi-Pure to help reduce the 'icky stuff' along with a trickle filter/sump connected to a refugium designed to flow through the substrate and then into the sump area (two overflows, one return pump). The 'fuge area has one chamber with chaeto and one with live rock, macro for tang food, and a few mangroves. I realize the mangroves aren't really doing all that much, but hey- every little bit helps! Check my gallery for pics. The main point I'm trying to make is that you still need some sort of nutrient export to take care of by-products as well as some fresh nutrients. I've used the SeaChem Purigen before also- it works really well as well. I recall a reading about a test tank using the Boyd's which has had no water changes in 5 years- and they breed clownfish in it!