2 gallon aquarium

Question
i have a few questions about a 2 gallon tank that i purchased about 3 days ago. I conditioned the water, and circulated it for 24 hours before adding any fish.  Yesterday i added 3 small platies, and early this morning i added a mystery snail.  All yesterday and early this morning the fish were very active and swimming around and the water was crystal clear.  The fish ate fine and ate all of the food.  I went out for a few hours and when i got back the water was cloudy and the fish were sitting at the bottom of the tank.  They still have random "swimming sprees" if you will where they are very active but in comparison to yesterday they seem lethargic.  This is the first fish that I've owned besides a betta or guppy/tetra.  I've been very successful with these, but I've never had a filtered tank before.  I checked my PH and ammonia levels, which are both perfect.  What could be causing the cloudiness and how should i go about cleaning the tank?  100% water changes or 25-30% water changes? How often? Thanks for any help you can offer! -Jessica  

Answer
Hello Jessica,
2 Gallons is tiny for any fish, so if you want your fish to be at all happy and have less chance of them simply dying, I would buy a 10 Gallon minimum tank. This also gives you a bigger selection of fish to choose from.
Before you put fish in a tank, you need to cycle the filter, so it actually works. You need to buy pure bottled ammonia, and add it until the ammonia levels reach 4ppm (never do this with fish in the tank, buy the bigger tank, cycle it, then move the fish over) before the ammonia slowly drops. The nitrite will raise, and lower, and eventually, the nitrate will do the same. When the nitrate is at least 40ppm, do an 80  water change. You are then ready to stock your tank. It seems complicated, but you should be ok. Ask me as many questions as you want, and you can email me at kathrynhaldane@yahoo.co.uk for an even quicker answer if you need help quickly or just can't be bothered coming onto this site.
Anyway, here's a bit more information about fishless cycling a tank:
http://fins.actwin.com/mirror/begin-cycling.html
http://freshaquarium.about.com/cs/biologicalcycle/a/nitrogencycle.htm

When the cycle had finished, the ammonia and nitrite should both be 0.0, and the nitrate should be under 20ppm.

Until you have a bigger, cycled tank, they will probably not look fully well. There are no fish that can live in a 2 Gallon tank.
Until you can get a bigger tank, just do 20 - 30 percent water changes every couple of days.
When you have the bigger tank, never do 100  water changes, just do 20 - 30 percent changes every week.

Good luck,
Kathryn

Feel free to ask as many questions as you wish.