is 192 watt PC's enough to house clams


It all depends on species and size:

ON VHO and PC I would keep Derasa and Squamosa.

IMO, Nothing beats Metal Halide. It is the way to go.

I'm not saying that you can't keep any clams on NO, VHO or PC.
I've tried them all and the best results came from MH.
I agree that some clams can be kept under VHO or PC but in my opinion you don't have enough light for any clam yet.
so one of those 175 watt metal halide will work for my 3 foot long and 1 1/2 feet depp 40 gallon, i must know cuz i dont want to wate any money. :) i must know for sure. SO im not gonna need any antic PC's or anyoter lighting this will be fine right?
I think the rule of thumb is that it will light a 2x2 foot square. I am sure that you can place clams directly under it and do fine. The ends of your tank may be dim and the actinic supplementation is mostly for aesthetic purposes. Color is up to your own personal preferences. But a clam can live under a 175W MH. Keep in mind there are more critical variables than just lighting to keep clams happy. ;)
You could keep some types of sps on the top rockwork w/ the 175. A 250mh would really be ideal for your tank, and won't cost that much more money.