Hi there. People here have given great advice already regarding your anemone and clown situation. While it is doable to keep an anemone is a small tank such as your 16 gallon, it will either do one or two things: outgrow your tank very fast and kill other corals if you do have them in the tank. While I don't recommend it, I have seen 12 gallon tanks with Heteractis crispa in them, and albeit a species tank. However, this tank has a larger sump and so the water volume in respect is much higher than your 16 gallon.
You have to understand that in our 'viewable boxes', clownfishes do not need an anemone to survive. In fact, survival records of anemones are still low, even counting the arguably common bubble-tip anemones. There really are no "easy" to keep anemones. Salinity and temp fluctuations, IMO, are very detrimental to keeping anemones alive. The other important aspects of course, are feeding and lighting. I am by no means telling you not to do it, since that is your choice, however, there are other options. Flowerpots, vases, a coffee mug, are just some options. In fact, you can get pretty creative.
On the other hand, a pair of true perculas will be fine even in a 10 gallon tank. I do not recommend it, however, as a 10 gallon tank gets rather dirty fast. If you are looking for another true percula, shoot me a PM and I will steer you in the right direction.
Best,
Ilham