5.5 gallon and 20 gallon

Well, adding the plants in while cycling you tank is definitely gonna help the process as live plants eat up ammonia and other harmful things. With a 5.5g tank, you could do one betta along with some shrimp (depending on if he's a calm or aggressive betta will decide how that goes). Another option for that small is a small school of Celestial Pearl Danios, but nothing else. I would go with the betta because 5 gallons is a little small for active swimmers. And I'm sure lots of other people will have some cool ideas fpr that 20g you have Welcome! I wish you well in your creations!

I have a 20 gallon set up myself, running double filters on it, planted. I did a fish in cycle, since one filter was already cycled. Never do fish-in cycles. But I had no choice... But you could do a few things for a 20, such as a nice school of Neon Tetras or Rasboras, with a Dwarf Gourmai as a centerpiece fish and a few Otos or panda cories as bottom feeders.

I prefer the 20g long because I like to make riverscapes, and the length is helpful. If you are going to do neon tetras (I assume that is what you mean by neon glo fish) they are small and tend to be at the low end of the food chain - most larger fish like to have them for dinner! They are happier, and more interesting to watch, in schools so 7-8 fish is a minimum. If I do a community tank, I like to think in terms of which fish are top feeders, middle feeders and bottom feeders. That does not guarantee that the fish will always stay on the top, in the middle or on the bottom but it does increase the chances that there will be fish scattered throughout your aquarium, making it more interesting to look at, though a little more challenging to feed (Note: please make sure that the fish are naturally "neon" and not injected with some kind of dye to make them look like it. In my opinion, any fish shops that sell the imposters should be boycotted.) Are you going to plant the tank?

That much said, I would stock using some hatchet fish - top feeders, the neon tetras - middle swimmers, and some cories or kuhlie loaches on the bottom. Active kuhli loaches are also fun to watch, though I have yet to figure out how to choose which ones will be active and which ones not. The numbers of each are going to depend on how many of the others you buy, as well as how many plants you put in the tank. None of these fish grow to be very large, so you will have a happy family of fish, once they are established. Way back when, before I used plants, I used to use a RUGF and 2 hang on the back type filters - enough filtration for a 50 g tank, even though it was only a 20L, that let me stock the tank beyond the normal rules.

Your 5 gallon? How about some shrimp, snails and dwarf frogs? If times ever get tough, you can always turn up the heater and have seafood soup

I just started keeping rasboras and already am very fond of them. Colourful active schooling fish, in my opinion, are a must in a tank between 10 and 50 gallons, especially if you are a beginner fishkeeper. Easy to care for and extremely fun to watch shoal around. True rummynose tetras are another favourite of mine, the red noses and zebra striped tails look great in almost any tank.

As far as bottom fish go I really like cories, watching them sniff around for food is very cool and people always exclaim in delight upon seeing them for the first time, especially kids.

its really up to you- you can have a very nice stock of fish that are under 4" in size as long as the filtration is adequate and the water has been cycled properly. Live plants do wonders for water quality and speeding up the cycling process, and again in my opinion are far more suited to a community aquascape than fake plants. Some fish are incompatible, but as long as you ask here any of us can point you in the right direction.

Just don't be suckered into seeing an amazing looking small fish and impulse-buying it: do the research and make sure the aggression, size and water quality requirements are all suitable for your tank. Its no fun buying a fish and then finding out its going to turn into a foot long monster that will look upon the rest of your tank as a snack (or get stunted and die horribly after eating your fish). Also be skeptical of what pet store employees tell you, sometimes they just want to make a sale.