johnptc;1754969; said:why notonce the nitrates are gone you either need to add or subtract minerals and trace elements
whats missing ???
ps welcome to mfk !!
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Thanks for the welcoming. However, as far as adding trace elements, you would have to continually be adding these trace elements and test your water at all times to make sure you have it balanced. Keep in mind, the reason for the "closed system" is to take away the hassel of water changes. By having to constantly monitor, test, and add things to your water you are only creating a new job. So, it would just be pointless. The idea behind closed system filtration is to already be replacing these trace elements without having to add any yourself. Think of it this way, I don't condition the stream in my backyard, yet it seems to support aquatic life.