Lucy I would opt for an LED strip - pure white 6000K as these will aid plant growth. You can also cut the strip to the exact size and will bring out the colours of both frogs and flora. Here in the UK, bills are very high so by opting for LED, you are in theory saving yourself a good few quid over the years to come. The profile is also only a few mm in height. Depending on how you choose to fit this, go for a waterproof version and play the safe game. With regards to your false bottom being 30cm, this seems a bit too much. By reducing this to 20cms, your giving yourself more room to play with... not to mention the frogs appreciating more room to explore.