I am surely no expert but I seem to remember reading that mineral h2o wasnt a good substitute for tap cause of varing mineral contents
two gallon with 16 gph filter with live plants and a female betta named Meloday
3-4 gallon with 80gph ... Planted lightly three white clouds ( Birtha Clara and Delila) and some snails (mainly melodys snacks)
9 gallon with 130gph , heated with male betta (Trafalger RIP)Kaden ( a male betta)has moved in, pygmy cory (MaMa) , pitbull pleco(Metal), three preacox rainbows( Annabel, Glitter and Mondo) and various snails...
I have just bought a 10g tank (space a premium unfortunatly). I think my tap water is extremly hard and when I filled it there was alot of 'scum' on the surface (limestone or calcium deposits maybe) so just wondered about using mineral water as an alternative.