Yes, I use Prime each time I do a water change.
I've just read what you've said and actually i think you have got guppies which are now stressed with the danios and any alterations is making it worse for them..don't you have a friend or anyone who can take them off your hands and re-home them.I’ve done that and they seem to be exploring but then going back to their hiding place. If I approach the tank, they immediately go straight back into hiding
That would be the best case results if the danios could be re-homed or placed in another tank. All their activity is stressful to fish like guppies, add in bright lights and lack of plants and background it all adds up. You can try the suggestions on lights, background, plants and hiding spots and they may help the guppies but the Danios are still going to be active.
My son in law as danios but he's got them mixed with platy and other fish their own size so it takes down their activity...until they are removed those guppies will hide or keep well away.
What a shame, as you can have danio's as cold water fish if you had a spare pump you could move them to a tub or something just to ease the pressure from your guppies.
