No, this is not suitable for an aquarium.
First of all, it is more expensive than a five stage RO/DI system, it doesn't use standardized cartridges, so you will be paying more over time to replace these filters. Standard RO/DI systems use standardized cartridges which you can buy from many different places, not just your reef aquarium mega store.
Secondly, one of the five stages is a 'remineralization filter' which isn't a filter at all, but actually puts certain metals back into the water for taste. You absolutely do not want it putting stuff into your filtered water. Heck, you probably don't really want it even if you use it for drinking water.
So in essence if you buy this you are paying more for a worse filter, with the upshot that it has a convenient countertop form factor.