I have three very small Figure 8 puffers in a 10 gallon brackish tank (which will be upgraded when their size demands) and they spend a lot of time swimming into the side glass. The tank is not sparce by any means, it has loads of rocks and obstacles littering the tank - my question is, do I need plants (real or plastic) for them to swim around? Would having more than one puffer in a tank make them uncomfortable? The LFS approved of this set-up - is this behavior of swimming into the glass just a natural quirk of puffers?