I think it's the same basic principle, but on a larger scale. From what I know (limited) some fish are particularly sensitive to small amounts of impurities and so benefit from having RO water, but hopefully someone will elaborate on this a bit for yiu.
TROPICAL TANK-Elite Tank - 207litres
6 Harlequin Rasboras, 5 Emerald Eye Rasboras, 10 Cherry Barbs, 2 Bristlenose Plecs, 2 Panda Corys. 4 Dwarf Chain Loaches.
ViaAqua Tank AR620 97litres
1 red male betta, 1 BN