Thank you so much for this reply, its really helpful.
Love the pic's of the tank, has given me some real inspiration

Presently using a 17 gall tank that I used to keep fish in, and the 4 guys I just put in there seem to be just fine... exploring and 1 even seems to be 'playing' on the log waterfall I put in... keeps climbing to top and then after sitting on side for a while (?to get his breath back??) then moves to sit in middle of the flow and eventually 'slides' back down into water... lol.... so funny to watch
