How about keeping goldfish and feeding it earthworms? Goldfish is only four centimeters big.

It is ok to raise goldfish to feed insects, dragonflies, red nematodes and the like. If it's too long, you can cut it. Hey! Clean up the bottom of the water if you can't finish it at night, otherwise it will be easy to get muddy water.

Scoop out the water with a cup and slowly pour it back from the top. This will only increase the oxygen content in the water for a short time, but when you stop, there will be no oxygen soon! When goldfish float in a large area to absorb oxygen, it means that the oxygen in your water is almost gone (mostly in dog days, summer and night). Long-term goldfish in such an environment will make goldfish easy to get sick and even suffocate.

It is best to feed goldfish with live worms, followed by granular feed (high-priced feed is the best, red and green 1 is poor in 2 yuan, which is easy to muddy), followed by bread cores (oil-free parts) and steamed bread cores, and cooked food is not recommended. After all, goldfish are not carnivores and have no good teeth to bite meat! It doesn't absorb well!

For details, please refer to my previous answer:

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I hope my answer can help you!