Pregnant fish and weird bubbles

Question
Hi Chris

i hope you can help. i have males guppies, female balloon guppies and neon tetras in my tank. I started my tank back in sept 07 and have been very fortunate with it (not many deaths at all thank god!). one of my fish (or could be a few) keep having babies. I can't work out which one it is though and i am confused unless they cross breed? how can i work out which is pregnant? the do not really look like any of the others and a lot keep having yellow heads with big black eyes and a black body (they are beautiful!)

Also, which is the thing most annoying for me, i noticed this eveing that my pearl balloon molly has this bubble chain coming out of her? is this her having babies? or what else could it be? she is happy enough, still eating and swimming about

Hope you can help and thanks in advance

Chantelle (UK)

Answer
Hi Chantelle;

Tetras are egglayers so their eggs would most likely be eaten before they hatch or the the newly hatched babies would be eaten soon after if they managed to escape for a short time. Both your guppies and mollies are livebearing fish but they can't interbreed with each other. If the only female livebearers you have are mollies then they could be the mothers of the babies even if you don't have males right now. Livebearing female guppies, mollies, platies and swordtails can actually continue to have babies for a year or so after being separated from males. They have the capacity to "store" the sperm inside their bodies for use later on if males aren't available.

The "bubble chain" is probably her feces with gas bubbles in it. It is often from constipation. To help avoid constipation in the future, give your fish veggies. I give mine cooked peeled peas, romaine lettuce, cucumber slices and cooked shredded carrots. Feed them 3 times a week in place of a regular meal. It's good for all your fish. It may take a few feedings to get them used to it, but keep trying. They will eventually 'dig in' like mine do. ;-)

At Your Service;
Chris Robbins