To close the loop here, I did use 100% silicone clear sealant, which is labeled aquarium safe. I piped it into the inlet chambers using the long nozzle that comes on the tube, then inserted a chopstick with a q-tip taped to it, and gently smeared the insides of the chamber. After wards, I used a toothpick to poke out the holes where the water comes out in case I had blocked them. It set up for two days, and now works perfectly, with no leaks.