We do not clean ponds or lakes,but an aquarium needs to be cleaned.why

1.	We do not clean ponds or lakes,but an aquarium needs to be cleaned.why?
Answer» As aquarium does not contain soil or decomposing bacteria which helps to convert the complex organic substances to simpler organic substances which helps in decomposing the same in soil which acts as a cleaner. there is need to clean aquarium bcz it is not a self sustained ecosystem. waste in aqua. can\'t be decomposed as microorganisms in it are not active..... all these is vice versa in ponds or lakesssss........??

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