I Have

[OohFeeshy]

Whether you have harlequin rasboras or not. There is a topic of yours about having a dead harlequin, which obviously makes me think you have them, although were they what you got today? You didn't get tetras too did you? How many harlequins do you have, did you buy anything else.

Your fish have different water requirements. The livebearers(guppys,platys) need hard and alkaline water, tetras and harlequins the opposite.

Fish are very adaptable, but this is the least of his worries. Most fish are adaptable to any tap water on offer.