You'd be surprised. It's far better to give the fish the tank size they need from the outset. It will look healthier and grow faster. Look at it this way, at what point does the 10g start being detrimental to the fish? How can you tell? It will start to become stunted but you might just put it down to slow growth. I'm almost beginning to think that putting your GSP in a larger tank might well solve some of your issues.
