Platinum Convic/fish

Question
On the 18th of March I began a new fresh water tank. I purchsed three dalmations and two little neon fish and I added with them my two convics form the other tank, along with the cat fish.  They all seem to be doing well in the begining, however when I got this morning one of the convicts was laying lifeless on the bottom of the tank. There has been some weight gain over the past month or so. It was much bigger than its companion and I purchsed them together about 15 months ago. Was my baby sick, pregnant, or was it the change.

Answer
Good evening Natisha, thank you for your question.

Have you tested your water quality? Unless you added the instant cycling product Bio-Spira, your tank is not cycled. Adding media from another tank speeds up the cycling process, I hope you put a used filter cartridge on the new tank's filter, and used some gravel from the other tank.

In a cycled, healthy, established tank, colonies of beneficial bacteria on the filter media and substrate, break down fish waste (excrement and uneaten food) into a less harmful substance. Ammonia turns into nitrite, and nitrite into nitrate. Both ammonia and nitrite are toxic to fish at any level. 0 ppm is the only "safe" level, even half a point is toxic. Nitrates should be kept under 20 ppm, with as low as possible being ideal. Do a water test right away if you haven't already, to confirm that these levels are safe.

Please remember this site for reference:
http://freshaquarium.about.com

Everything you need to know about aquarium startup is there. How to clean a fish tank, move a fish tank, what kind of equipment you need - it's all covered. In the meantime, if you have levels of ammonia or nitrites showing up, you'll need to do a massive water change to dilute the levels in your tank, about 75%. With dechlorinated tap water!

After that first large water change, test your water again. Water changes from 10-20% a day will need to be performed. These water changes prolong the cycling process, but are necessary to keep your fish alive and healthy, and eating.

A few other things...

Convicts are extremely aggressive fish when spawning. It doesn't sound to me like your female was/is pregnant, laying on her side does not sound like spawning behavior, it sounds like a reaction to water quality. Convicts have been known to kill everything in the tank when they set up a spawning site. It would have been much better to leave them in the tank they were in (20-29 gallons is ideal for a single pair), especially since the neons will be consumed by the convicts in short order. South American cichlids such as convicts prefer softer water than mollies, who prefer harder water with a pH above neutral. Mollies need either very clean fresh water, or brackish water, otherwise they are an "ich magnet" - they are highly susceptible to whitespot disease, or ich. Not having quarantined your new mollies, I would be very watchful. Having aquarium salt in the tank helps, but none of your other fish will "like" the salt, so it is a catch 22 here. Also, there are thousands of species of catfish. Some of them, like iridescent sharks, grow to 40" while some, like the upside-down catfish, do not grow above 4". Both of these are "catfish" - iridescent sharks are not really sharks. So you see, without more specific information (i.e. what kind of catfish this is) you'll never be able to research its care requirements. Many catfish also love to make a meal of tiny fish such as neons, preying on them at night - most catfish are more active at night. See if you can find out the common name from the pet store, and begin researching the catfish for both of your sakes.

I encourage you to do a bit of research before you buy any fish. Your community is not really compatible. This sort of trouble can be avoided by just reading for a few minutes about the species you are interested in keeping before purchasing them. Another site I like to refer my readers to is this one: http://www.wetwebmedia.com

Another question and answer site, it is searchable, but you can find out lots just by browsing. You can also look up profiles for specific fish by using any of these sites:
http://badmanstropicalfish.com
http://fishinthe.net
http://www.fishprofiles.com

Google.com is considered by most to be the best search engine out there. Please use it for research - I probably do several tens of times a day! Most importantly, do not depend on the pet stores for advice. They will sell you expensive, incompatible, and difficult to keep fish in a heartbeat. It is very near impossible to succeed at this hobby if you don't read about it! I hope that helps.

Good luck with everything,
Nicole