If this is a brand new tank you just set up did you declorinate the water? You may also want to do a Google search for Nitrogen Cycle. If you give more specifics I may be able to offer other suggestions.

I'd suggest you pick up a copy of "Aquariums for Dummies." It is a great introduction to aquariums, biological/mechanical/chemical filtration, water quality, and a host of other issues involving setting up your first (and subsequent) aquarium (s). I've given it to my nieces and nephews, as well as my godson, before they started up their first aquariums. When you set up a new aquarium you should make sure your water has been treated to counteract the chemicals your water department treats the water with. If you are on a well or spring, this first step isn't necessary. You should have the aquarium up and running a couple days before you even think of putting fish in. If you have a friend with a healthy aquarium (ie, no sick fish or history of sick fish) you can get a sample of their filter media to *seed* your aquarium with beneficial bacteria. If not, it's best to let your aquarium run for a good week, before you introduce fish. When you do add fish, you should add them slowly. Add a couple fish and wait a week or so, then add more. This allows the aquarium to slowly reach a stable mixture of ammonia, bacteria and nitrogen. I've found, that it's best to start over from scratch, once you've had a major clouding, if you have no fish. One question... Was your aquarium near a bright light source (ie, in front of a window)? If so, the *cloudy* quality could be an algae bloom. Good look on your aquarium.

why to meany fish and frogs .get ride of some that should do the trick

It was a predictable event. Adding 18 inhabitants to a small aquarium suddenly would greatly over tax the biological filtration system! Death by poisoning is not a fun way for them to go. If a pet shop sold you all of those creatures at once, they are a VERY irresponsible pet shop! Did you set up the tank three to seven days ahead of time? If you had just filled the tank a few hours before, and didn't use dechlorinator, that is probably how you killed them. It places a pretty low value on their lives to not do any research before purchasing.

I'm a new fish tank owner so I'll tell you from a beginners perspective.And in plain English. Before starting you need to purchase clear water, a pH kit,stress coat, filter(for your gallon tank),all found at a pet-co or pet-smart and tell them your starting a tank and need the stuff that purifies tap water.Make sure you soak and clean your rocks prior to use. Put in rocks and decorations, fill tank,hook up filter. Let filter for 24hrs. Then take blue cartridge out of filter and put in all your mixtures this is to clear cloudiness, purify tap water, and give your tank the slim it needs. Now let filter for 24hrs, replace blue cartridge, test pH level set and check temperature.Filter for 24hrs.Now your ready for fish. DO NOT SET UP YOUR TANK IN SUN LIGHT VIEW IT CAUSES ALGI TO GROW RAPIDLY Before purchasing fish check to see what type of fish you like aggressive, semi-aggressive,community ect. Most of all only start with 2-3 fish at a time just to see how they take to your new tank then in 1-2 wks add another couple of fish. To many fish at one time in a new tank causes New Tank Syndrome. Change your tank's filter cartridge every 2-4 wks to keep a healthy tank. Good luck - need my further help email me @ m_annette_m@ymail.com

OOPS - double answered, but didn't realize it. Did you read a book about aquariums before killing them? Did you set the tank up for a week with the filter(s) and heater running? Your outcome was predictable. First, never add more than a few fish at a time! You will overload the biological filtration system. Too bad the pet shop didn't give you any information. Read a book, then come back with questions. Good luck.