Hey Lunchbucket,
Sorry it took so long for me to respond. The reason why I took the stand I did is based purely on actual personal experience (more of which, I think, is genuinely needed on 'the boards' - way too much parroting of "he said", "she wrote" etc). Nathan nailed it, in that lumens are what drives clam growth. I didn't start having real 'luck' with clams until I stepped up to MH, in addition to the VHO & PC lighting that I already had. That's right, I was running 570watts of flourescent over my 120 (4'X2'X2') and was still losing clams - much to my dismay - in a system where everything else was thriving. When I installed the MH I did so as to spotlight the area I was going to keep the clams in. The reason why I did this is because MH penetrates the water better in a localised area. You're not going to get the spread that you do with flourescent, it's more pinpointed. I placed my light pigs about 12" form the MH source. This corrected the clam mortality problem. Everyone was happy.
Everything was going great, until I got cute, and tried lowering a couple of my Pohnpei maximas in the system, in order to get a better top view on them. Now keep in mind, both clams are roughly 14" form the flourescents, and 22" from the MH (only 10" further away from the MH penetration point) in the middle of the system (the MH is further back on the tank). Both clams began deteriorating after only a couple of weeks because the light penetration had dropped that dramatically. Long story short - I lost one clam, and saved the other by moving it back up in the tank. So, all said and done, 820 watts of combination lighting, at 18" depth, was not enough PAR to keep my T. maxes healthy. I guess my point is this, you could try one, but man, as much as clams cost and as beautiful as they are, it would be a shame to lose one the same way I lost mine. Learn from my mistakes. Anyway, all the clams are rocking now, and are putting on size.
DJ
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