Yea Arkman that was the topic of discussion between me and Steve most of the evening. My tank is loaded with sponges, we counted 7 different varities, I think Steve got a chunk of most of them to, lol.
As with most things thier are many different types of sponges and each has different requirements and can survive in differing enviroments. With in all our tanks are tons of different ecosystems and our best conclution would be that the sponges are growing in areas that are skewed to thier liking. Alot of folks think that because you skim and use UV that you are killing all the bacterial/protozoan/planktonic life in your tank. Well that is not even close to the truth. Most bacterial/protozoan/larval and planktonic life lives and reproduces with in the crevises and confines of your LR and/or substraight, basically they are prey and hide to stay alive (thier smarter then we give them credit for. Most of the free swimming critters are what we call paralegic (or basically the stuff that is hunting the above list or is looking for a host. Water that goes through the skimmer and or uv's is basically taken from the open water column, so yes some of the good critter are laid to waste but most of them are the nastier ones. For me the getting rid of the nasty ones is really worth the sacrificing of a few good ones. When it comes to the larger critters, such as pods, worms and so on. My fish dont seem to mind if they come into the main tank fresh or cooked. Thier life span is still 1.5 seconds before a fish pounds them down.
In regards to the sponge box or tri zonal filtration it is something that I am not interested in doing, but again the use of sponges and squirts seems IMHO to be a real good idea, and one I think I am going to put in play.
Mike
