well if the cave u plan on makin is a bigger cave a true low intensity light shouldnt be to bothersome.. u can always test it be having it in the tank and testing it at night. that or have it on a timer and let them adjust to it being in the tank. have u looked into s oll me.of the pool/pond lighting for ideas? I know ots a completly diff scale size but even if its the wrong size it may offer u some ideas..and I know on fosters&smith they have small led lighting sets for aauariums, im just not sure of what ur after.