too many mollies

Question
Santa brought us a 5 gal. tank w/filter but no heater.  We have two mollies.  They don't look much alike, but they had 4 babies.  I now use water from the grocery, since a progression of fish died shortly after the tank was set up, and our tap water is not fit for human use.  We have lillypads growing in tank.  Just tonight I noticed white cloudy stuff all over in the gravel.  I cleaned the tank about 10 days ago, I replace most of the water each time I clean it, but I added water a couple nights ago.  I see the filter is not working well, need to replace that tomorrow.
Question #1  How do I keep these guys from reproducing?  
Question #2  What is the cloudy stuff?  Before reading up on mollies tonight, I thought it was eggs.
Question #3  Could I get a catfish or something to eat the babies before I feel bad about having to get rid of them?
Question #4  What would you put in a tank this size to keep a four-year-old kid happy?

Answer
Hi Sherry;

Mollies will reproduce no matter what you do. It's what they are known for. I sure wish I could help you with that one!

The cloudy stuff on the gravel is probably excess waste and/or food that became infected with fungus or bacteria. Vacuum the gravel and make a 25% water change to get it out. Cut back on food a bit too. Overfeeding is very common. We all do it from time to time. We just have to mend our ways and clean up after ourselves once we realize it. It is easier on the fish to replace no more than 25% of the water and do it once a week. Changing more water than 25% can shock them. All tanks really need a weekly water change to keep water chemistry and water quality consistent.

I can't really recommend a fish to eat the babies because your tank is actually already overstocked. Mollies should be in a 20 gallon or larger because of their potential adult size (3 to 4 inches) and their need to move around and get exercise. The parents will eat their own young anyway. Just feed them less food when babies arrive and nature will take it's course.

A community tank can have up to one inch of fish per gallon. You have to calculate based on the future adult size of each of your fish. This rule applies only to fish that get no larger than about 3 inches or so as adults. Imagine a 12-inch fish in a 12-gallon tank...yikes! It just isn't wise to apply the inch-per-gallon rule to larger and messier fish. You can go a little more than one-inch per gallon (as long as it's less than 2" per gallon) but be sure to maintain the tank weekly and don't overfeed. If you think you won't be able to do changes weekly, stock the tank very lightly with fish.

Some better options for your 5 gallon INSTEAD OF the mollies would be;

A male betta with a couple of little cory cats

Or;

A pair of dwarf gouramis and a couple of cory cats

Or;

3 neon tetras and a couple of cory cats

Or;

3 white clouds and a couple of cory cats

Cory cats are schooling fish so get two or more. Instead of cory cats you could have Otocinlus catfish. They eat algae. Or, get some ghost glass shrimp. Bottom feeders are very important in small tanks because of the high possibility of overfeeding.

At Your Service;
Chris Robbins