Couple Questions about Mollies and Platties

Question
Hi,                         

         My name is Chip and I'm 18 and i have a 20 gallon tank with i black mollie, a dwarf plattie, 6 three week old baby platties (in a breeding net), and a dalmation mollie.  I just had a few questions i was hoping you could answer if you didn't mind.

         First, when i bought the dalmation mollie about 5 days ago the lady at the pet store said she was pregnant and she would have the babies in a week or so i bought a breeding floatation device that allows her to have the babies in so she won't eat them.  But I'm not really sure if she is pregnant or not how can i tell?  She has small yellow dots around her stomach and its kind of big...

        Next, I was wondering when i could let my baby platties into the tank?  They are about 3 weeks old and the size of my finger nail.

        Last, I was wondering what are some tips on how to get nitrite out of the tanks system? It is at about 7 right now and i have been changing the water weekly and putting aquarium salt into the tank recently but it doesn't seem to be working too well..


                                         Thank You so Much for your time,


Answer
Hi Chip! (thank you for your well-written letter!)
Well, first off most likely your Dalmation Molly is pregnant. Most mollies you buy at petstores have already mated in the petstore and they will usually deliver fry within a few weeks. Most mollies "drop" a brood of fry about once a month or so. You can easily tell when they are pregnant as they will have a very rounded belly, which may even 'square out' in shape when they come close to birthing their fry. When she starts looking this way you probably want to move her into the floating breeder trap.

Your baby platies could probably go into the tank. Just watch them and if they are get excessively chased they may need a little longer to put on more size. They should be fine but you can't know until you try.

Do you mean nitrite or Nitrate? If you really mean Nitrite then your bacteria must not be working efficiently enough to keep the nitrite under control. Maybe the tank isn't fully established yet or something interfered with the bacteria like an overcleaning of filters, ect... If nitrites are the case then you'd need to make sure your tank also doesn't have ammonia, make several large water changes and maybe try a bacteria additive (such as "cycle") the nitrite should drop on its own also with some time.

However, if you mean nitrate (hopefully) then all that is needed to keep this under control is just frequent water changes. Sometimes it is necessary to do twice a week water changes then just once a week.

I really hope this helps!
Best of luck and happy fishkeeping!
Karen~