My tank evaporates about 3 gal a day with approx 15-20 pods in my sump it was 3 gal a day before I added the pods.Its been cold lately so if your house heater has been on that will also contribute to evaporation. Pods acclaimate better if they are in the sand but you can wedge them into your rockwork. Metal halides may be abit to intence for your pods if they are to close to the light. Mine are in my sump w/ 75watts on them and they are growing like mad.

Barry