Sounds great so far! Is it possible to have a snail, a handful of shrimp and a Betta in a 5 gallon?
I don't actually have the 20 yet, I am still in the "thinking about it" phase on that one (and keeping an eye on CL and Freecycle). When I do manage to find one though, I am definitely going to go for the Glo-Fish.Ultimately, the fish Hobby industry is about money. Just because Bettas can be kept in a small amount of water they are, to keep the price down. We do not give fish choices. Fish are plunked into a tank and learn to cope or die.
Bettas are, along with Goldfish and Cories, some of the most ill treated creatures.
High temps (80 plus is good) and some cover as well as clean water are all that are needed for this little predator to shine. Do they show characteristics that appeal? You bet!
Danios are a good choice for your babys twenty as is a Betta, Snail(s) and some plants in your five. Shrimp are a crap shoot; depending on the Bettas personality the Shrimp may be hunted down or ignored. Try the Shrimp and see.
Kitchens are potentially hazardous places for tanks so think of the tank when doing Kitchen type things. Small (25W) heaters are available at Wal*Mart for very little money so unless this is covered this is a good hint. Be aware that the tank should be on a GFCI. GFCIs can be irritating but they are also a potential lifesaver.