Water readings after adding new fish

[Travis32]

Just seeing if this is normal. After my tank cycled with 5 zebra Danios AND seeded sponge from another aquarium, I added 6 cory catfish around late afternoon. Very early next morning I tested my water and got 0 ammonia, 0 nitrites, and 20 nitrates. Then the very next day I tested it again and got the exact same results. A week later I added 6 Bosseman rainbow fish, and the same thing happened very next day all the readings were perfectly good. It has now been 3 days since I added them and everything is still perfect. I know that the numbers I just described are exactly what I want to have happen. My question is, is it normal for your tank to fully get back to good levels that quickly after adding fish? Does that mean that my filter has a lot of very good bacteria in it that can filter it out real quick? Thanks for any advice

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[Glene20]

What size is your tank and what filter are you using. Your filter may have enough good bacteria to break down the ammonia. But its best to only add a few new fish at a time ao your not over running your filter. Seems your doing fine ☺

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[Travis32]

Sorry, 75 gallon. Marineland Emperor 400 AND Marineland Penguin 350.

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[ScotJudd]

There's your answer Travis, you're running a 75 gallon tank and increases in ammonia will be diluted by all that water. I wouldn't try the same with a 20 gallon.


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[mrvincent]

Maybe the ammonia get too much diluated in that big tank water volume... So you don't get readings. Plants may be consuming ammonia too..