[judya]

I didn't think platies got that big. I know swordtails and sailfin mollies do, but platies?

As far as cycling, the critical thing is to stock your tank VERY slowly - a couple of fish now, a couple of fish in a few weeks. There are little bacteria in the water that convert fish wastes (ammonia - harmful to fish) to nitrite (harmful to fish) to nitrate (not very harmful to fish). This will happen naturally in your tank, but does take some time for the bacteria to grow and multiply enough to handle the fish waste. Everytime you add more fish, (or too much food) the bacteria will multiply to handle it, but again it does take some time. When people say a tank is "cycled" they mean the tank has enough bacteria to handle that amount of fish. However cycling is a process, and everytime fish are added, it will have to grow a few more bacteria.

To remove the nitrate (the end product of the cycling process) it is recommended that you do some water changing. This pulls out the dirty water, and adds fresh water. A suggested amount is 10-20 % every week or two. However, more is better. Just make sure the new water is the same temperature as the tank water, and that you treat it for chlorine/chloramine before adding. You can use a siphon or gravel vacuum for this which pulls the gunky stuff out of the gravel as well as changing the water.

Make sure you have a bucket that you only use for fish. Nothing that would have floor cleaner or anything else in it.

The only test kit I recommend is a pH test kit. If you check the tank every week or two, you will see if it is holding steady. If it starts getting more acid than before, you probably need to do a water change.

A nice fish for a 10 is a corydoras catfish or two (they like to hang out together). They are cute, non-aggressive, and will pick up the food that falls to the bottom (No, they don't eat fish wastes, or algae).

Also when you buy fish from the store, 1) make sure nothing in the store tank has little white spots on it (ick - looks like grains of salt) and if their tanks are on a central system, don't buy any fish that day. 2) float the bag of fish in your tank for awhile to get the temperature the same 3) open the bag and add some tank water to the bag - a little at a time, so the fish gets used to your tank water gradually. That is one of the key things - change should be gradual (water changes, moving fish from the store to your tank, etc.)- otherwise the fish will suffer and maybe die.