Can't see the dorsal fin properly. If it's Hypostomus, it'll have ~7 soft rays in the dorsal, while Pterygoplichthys has upwards of 11.
In either case, these are too big for 125 litres, at least when more than about half-grown. Even a 180 litre system would be pushing it, and you'd need 250 litres to be comfortably housing these fish. It isn't so much water quality (at least some of these fish are incredibly hardy) but simply keeping the tank clean. They make huge amounts of solid waste, both faeces and plant detritus such as broken leaves and wood chippings. So you need a big tank with super filtration.
Cheers, Neale