Glofish are genetically altered Zebra Danios and as such require the same care. So yes they like all fish require filtered water, (even bettas strongly benefit from a gentle filter), but they are not tropical fish. The proper temperature range to keep glofish/zebras is 65-75 degrees, so you can get away without a heater but the steady temperature from having one is always a good thing. Zebra Danios school, so you need atleast a group of 5-6. However regular Zebra Danios school with Glofish just fine, so you can mix and match to your taste (and wallet). The minimum suggested tank size is 15g, though a 20g long is better. They need space to swim, so about the smallest you might be able to swing is a 10g.
I say if you got atleast a 10g tank go for a school of the three glofish you want with three regular Zebra Danios. Not only will they school for maximum health but even the regular ones are brightly colored and attractive fish. If you have a smaller tank then 10g it'll be too small to keep a proper school, which in turn will reduce their health in addition to the challenging effort to keep a smaller tank stable and healthy. Not worth it then imo.
If you don't know about it I strongly suggest you read the link about Cycling your tank. Zebras are commonly used to cycle tanks with fish, but Glofish are a bit expensive to risk adding to an uncycled tank.
