question about decoration

Looks great, however I would split the rocks into two piles at each end and leave some open sand in the middle, otherwise one male may claim and dominate the whole lot....

Is it a 4ft or 5ft tank?

You dont need to go any higher than you have in the tank pictures, as long as they are distinct seperate piles with at least a foot or so between them IME....90g 5ft will make a great size tank for your trophs....you may even be able to get a third smaller pile of rocks in for another sub-dominant male as well. :thumb:

I would definately go for at least 20 in total....as for Synos, if you are interested in some young surviving from breeding later on I wouldnt, but would be fine until then. I have a few bristlenose in with mine and apart from wrestling over algae wafers they ignore each other completely.