life of fish

Question
Hi there ! Ashok Again ! Be prepared to receive mails from more often now. I have a community tank, 4 feet in length and a foot and qrtr in width and height. All these years, I found that small fishes like mollys, guppies, tetras do not live very long. But fishes like angels, sharks, (bigger fish in general) live healthily for even years. Any known reasons? Is there any way to keep them both? I would like to keep some live bearers in the tank, which would supply live feed for my angels, as our home is a vegetarian home.

Answer
Dear Ashok,
A big hello again!

It's difficult to know exactly why smaller fish such as tetras wouldn't live very long. Sometimes it's because smaller fish are much more sensitive to water quality issues and illness. While larger fish tend to be hardier. But if water quality isn't the issue (poor water quality like the presence of ammonia or nitritess. In healthy aquariums, these levels should always be ZERO and nitrate less than 20) Then it could simply be old age the reason you are losing the smaller fish. Of course smaller fish usually tend to not live very long. Sometimes at the most of 2-3 years in some species like Guppies. And sometimes smaller fish live even shorter lives. Most small species, however,  will live for several years at least.
There shouldn't be any reason why you can't keep livebearers together with bigger fish. They should do just fine. And the Livebearers like platies, swordtails, like mollies would definately supply live food for your Angelfish and other larger species.

Also maybe it's your current source that has bad batches of fish sometimes. This can certainly happen sometimes and switching to a different source of fish may allow you to have better luck.

I really hope this helps and always feel free to write with anymore questions!

Best wishes and Happy fishkeeping!
Karen~