Yes you can put a single betta in a 20 gallon tank but i would put some other fish in with him. So long as they are not fin nippers he will be ok some tetras and perhaps some corydoras catfish. Check out www.kgbettas.co.uk hes got some stunners coming soon from Thailand.He is on holiday at the moment but he will send them local fish shops tend just to have the boring red and blue bettas. In the far east the males are all grown on in jars and they get 100% water changes every day to grow them on really quick. because i breed them myself i grow the males on in 2ltr pop bottles just cut the top off. You could have several males by setting up your 20 gallon and keeping the males in 3 litre coke bottles in the tank. Get you bottle and melt some small holes in the sides all around the bottle, i use a fork heated up on the gas(dont use it to eat afterwards tho)Place about 1 inch of gravel in the bottom and then fill your tank up. If you have say 10 bottles in the tank you could have 10 males and the water would circulate through the holes in the bottle. you could have a small internal filter to filter the water and push the current around to keep the water in the bottles fresh. Check out one of my spawning clips on youtube at http://uk.youtube.com/watch?v=jSlfJacIRNU
also check out www.bettatalk.com Faith is totally outrageous and one of the worlds leading authorities on bettas shes even been on the tele. There is also the uk betta forum for great advice form other betta fanatics

Have you got any photos of the perfect tank setup? That website had loads of photos of fish, but none of the actual tank. I think my 20 gallon tank would be perfect for a betta and maybe two or three other fish. I'm thinking that if I only have two or three fish, including the betta, the water conditions will not deteriorate too quickly.

And how much can you expect to pay for a good quality one

Because my set ups are breeding ones they will be different so i dont have pics of set ups if you go to the uk betta forum im sure you will find some to give you some ideas.

How about ultimate bettas? That's a pretty nice forum about these fish.

Previously, I've kept my bettas in large(five gallon) bowls, and sometimes in 10 gallon community tanks. Some people say that you can keep them in small confines(like bowl) because they live in shallow water in the wild. True, but these rice feilds are massive, and hold thousands of gallons in which the bettas move freely. Also, bettas dislike tall tanks-not so sure why though. Dinger545's idea of liter bottles in a tank sounds interesting. I'm sure they'd flare a lot. There's nothing more impressive in the community fish hobby than to see a flame crowntail betta flare.

There are actually three described species of betta, one of which i beleive is rarely kept in the hobby. The most usually found at the pet shop or your breeder is betta splendens. I've kept several varieties of betta splendens including the crowntail, and the veiltail.

Also note that many(not all) but many of the bettas purchased at a pet shop are adults and will only live 2-4 years. Babies and young specimens can be aquired from breeders and should live much longer if kept properly.

So what would be a typical tank for someone who keeps these fish? Do The real diehard enthusiasts keep just bettas in a small tank, or would they keep them in larger tanks with other fish?

Some of these biorb tanks look perfect if we just wanted to one fish. I've seen some that are 30 L going up to around 60 L.

Actually there are quite a lot more batta species that are available in the hobby now but some of them are quite rare. For a female betta pet stores will normally ask for around £2 and a male £4-5. For a female from a breeder it will be £4-6 depending on what colours and what finnage for a male between £6-12 depending on what colour or tail form. you will pay a premium for halfmoons. tank mates for bettas would be as i said before small tetras and corydoras set up would be a gravel bottom (clear if you intend to breed) decor as you like perhaps with some plants they especially like floating plants. They dont always spend their time at the top of the water but they do need to go to the surface every now and then. Filtration should be slow moving Bettas are not suited to fast moving water check out the filers that i use in some of my tanks at http://www.youtube.com/watch?v=rj1Glx5anfM this is a video i made to show how to make them. If you want some real quality ones check this page http://www.kgbettas.co.uk/comingsoon.htm
get these and they will do what the song on the page says. kev is a top bloke ive bought form him myself even drove to stoke on Trent from Portsmouth to pick them up heres one of my recent additions