Both of those species should really be in a bigger tank. Minnows require a minimum of 60 litres and danios require a minimum of 90 litres. 22 litres is not considered an adequate sized tank for fish, despite often being sold as such, and is really only suitable for shrimps and snails. Also as both minnows and danios are shoaling species, they should be kept in larger groups, which a 22 litre tank obviously will not allow. My advice would be to either rehome them or upgrade to a bigger tank. Have a look at our
caresheets for more info on the requirements of the species you have.
Do you have readings for the ammonia, nitrite and nitrate levels in your tank?