Glofish Danios

[Sal23]

Hello,
I have recently bought 3 Glofish Danios (on Feb. 4th) and have them in a 20gallon tank.
I'v just had a break from taking care of 2 Tiger Oscars and haven't taken care of little fish in a long time.
I'm not sure how to keep them healthy besides feding them and keeping the tank clean.
So here are some of my basic questions,

1) Do I do water changes? If so how much and how often? (25% every two weeks?)
2) Feeding them once a day is alright? Can I feed them anything besides Fish flakes? (Can I boil greens, or ting cut vegtables, do they eat bloodworms?)

So, for my last question, I was wondering if my fish were sick. two of the three have slightly bloated bellys, no one else would notice them if they looked at my fish, but I just want to make sure they are alright.

INFO:
Fish were bought at a private fish store Feb. 4th
They are currently in a 20gallon tank
They have a Wisper zbio-Bag Filter system running
THERE IS NO CARBON RUNNING ( I haven't put the filter Carbon bags into the system because I wasn't sure where they were, But I've found them, should I use them if there is a possibility of being sick?)

 

[OldMan47]

Welcome to the forum Sal.
It sounds like you have 2 female zebras. Basic care is much like the oscars except that the food is obviously much smaller. They need the same water changes and cleaning and should be fed daily what they will eat in a couple of minutes. All small fish will eat blood worms but I reserve them as a treat only for my fish. A good flake or pellet food with occasional blood worms, daphnia and similar foods is a good basic diet for them. If the fish start swimming rapidly from one end of the tank to the other in a group, the heavy ones will be in the lead. These guys are egg scatterers where the males come along behind the females and fertilize the eggs. They will also go back after the breeding and eat the eggs if they can reach them. Any eggs that fall between gravel particles have a chance of surviving to be born.
Unless your water is discolored or smells bad, the carbon is really not needed.

 

[Sal23]

Thanks for the advice OldMan!
The fish will sometimes dart back and forth like that, I hope that is what's going on, that would be nice.
Thanks for the advice on feeding and cleaning aswell, that helps alot.
: )