general fish and tank care

Question
hi started our tank about for weeks ago .did the run in period .went to pet store and got 5 neons and one samurai fighter.lost 2 of the neons fairly quick have since done water changes ,about 20 %. and tank seams to have settled down and fish seam happy and are feeding ok.
but one of the remaining neons has developed a small dicolouring on its back white in colour although after last water change it seams to be recovering i have read on here about the white fungus and treatment but where do u get the treatment from?a vets? or do i see if fish keeps improving.tank is 60 litre tetra tank with tetra heater and filter.
thanks from steve and tina

Answer
Hi,
A "run in period" or "letting the tank mature" does absolutely nothing for the tank. It needs to be properly cycled, but because you now have fish this is what you should do:
Buy nitrite, ammonia and nitrate test kits, and test these every few days. Ammonia and nitrite are both very poisonous, do they need to be both 0.0. Do daily 10 percent water changes until it is 0.0. The nitrate is less poisonous, and is safe under 20ppm. Live plants help lower it.
When the ammonia and nitrite are 0.0, and the nitrate under 20ppm, do weekly 30 percent water changes.
You can buy fungus treatments at most fish shops. I recommend Melafix, as it combats all major diseases. You can also buy it online. Definitely treat though, otherwise you might lose the fish.
When he has recovered, buy a few more Neons, so you have at least 6.
Bettas, or Fighting fish, like the one you have, are very aggressive and territorial. If it is a female, she should be ok, but males are very aggressive. He is probably responsible for the death of your other fish, and you should take him back to the fish shop as soon as possible, or he may kill your other fish.
I recommend you join http://www.tropicalfish.site5.com/tfc/
as you can get tips on what fish to buy.
You should never just buy fish without any info on them, some tiny fish that look ok for your tank could grow 2 foot long within a year!
Have a look round your fish shop, and note the names of the fish you like. Then, ask me, or make a thread on the website I just recommended, and we will tell you if they are ok for your tank.
Good luck,
Kathryn