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[Dale]

I thought nutrients were food?

There is this generalization that everything grown in our tanks is light Dependant - thus making waterborne nutrients unnecessary. Obviously, with certain soft corals and filter feeders this is not the case (how much light do my chili coral and tube worms need to thrive?). I think many reefers kill off or emaciate certain organisms by running "too" clean a system. Why intentionally starve a nutrient absorbing/filter feeding reef? Again, it is a case of distinguishing the specific needs of the livestock we keep.

I actually operate my tank somewhat as stircrazy suggests but there are limits (chosen/unchosen) to the amount of skimming/export possible IMHO.
One problem is that it is impractical to dose a tank to the nutrient density needed for some general filter feeding species if one is going to decrease the density to zero once again each time (I'm assuming large systems here). My vividreef live phytoplankton costs $20 a bottle and doesn't go far when dosing approx. 75G.'s of water. Some might add a little, thinking it's enough, but once diluted and only allowed to circulate for a short period the effects on the livestock is minimal.
It is also assumed that all the species in the tank will be feeding when one doses the tank. In my tank I find the livestock open and close on their own schedule.
I also don't know if it's very easy to go from nutrient dense to pristine like a yo yo unless one sets up a skeletonized reef ala SPS dominated displays (I'm going for the lush jungle look). I think it is a good idea to skim heavily but, other "passive" forms of mopping up nutrients/nitrates is a good idea too. I'm aiming for that balance stircrazy suggests.
FWIW, My routine is to dose the tank 2 - 3 times a week. I tee off my return line so that the flow feeds back into the sump like a closed loop. I allow my tank to sit for several hours and then return flow to the display. Display water movement is maintained by a closed loop circ. system.
I am slowly going B.B. (siphoning substrate out with each P.W.C.) mainly because my recirc sys. kicks up too much substrate when the blenny skates over it. I chickened out of B.B. initially because I wanted the substrate to cover my PVC piping but now I am confident that the coraline algae will look OK. One problem with going B.B. is that you lose the natural buffer that the crushed coral affords (I planned ahead for this by adding C.C. to my R.D.S.B.) Of course you can also counter this by using additives or a reactor. I also think one loses some sand borne scavengers that may aid in waste control (also not a problem if rock work access is planned for regular siphoning).

Whew!!! What a lot of work. May be those F.O.W.L.R. keepers know something I don't
________
herbalaire vaporizer

[StirCrazy]

Originally Posted by Dale

One problem with going B.B. is that you lose the natural buffer that the crushed coral affords (I planned ahead for this by adding C.C. to my R.D.S.B.)

Don't worry so much about losing this buffer, there was a test done years ago with a BB a crushed coral and a DSB tank left to crash. the BB crashed first but it was only two weeks later when the DSB tank crashed. If I remember right the time frame was over a couple months.

even if it did help though, with the PH your water would have to drop to to release any significant amount of Ca you are going to have bigger problems than low Ca. Also if it did release Ca you have to think of all the other stuff bound in that sand, Phosphates, ect.

Steve