My "cycled" filter turned out to not be so cycled after all so would love to discuss your thoughts

[rob_dixon]

Hi all.

In preparation for a new planted 20 gallon tank, for 5 weeks I ran an Oase 350 on a very well cycled 1 year old 14 gallon "lightly planted" tank with no fish, as all my fish had been moved to another tank.  (When i added the new filter I turned off the old one).   There was still plenty of detritus in this old tank to decompose and create ammonia, but as there were no fish now, in addition I occasionally dosed it with a few drops of Dr Tim's ammonia chloride to help feed our little helper bacteria friends.

Of course I tested this tank and sure enough the ammonia would drop to "0" overnight, a sign in my mind that the tank was cycled.   In short an attempt was made -  I wanted to give my new tank a head start as the soil i use leeches out a ton of ammonia.  I thought 5 weeks was plenty, and testing "confirmed" it was ready.

BUT when i moved this filter to my new planted tank, it seems the filter is not at all very cycled, as I am reading high ammonia still.  (0 nitrites, and 0 nitrates) - almost as if the 5 week "pre-cycle" was pointless.

I am curious as to what may have caused this result? 

[AndEEss]

A few drops of ammonia in a 20 gallon tank is not enough to properly cycle it. When I cycle a new filter, I calculate AND test to confirm that 2ppm ammonia have been added to the tank.

Also, when you use liquid ammonium chloride, it can cause a drop in pH over time, as it depletes KH. So you'll have to add a bit of something (baking soda, etc) to increase KH to keep your pH up above 6 or so.

 

[TOtrees]

Here's my thoughts: It's not time that cycles tanks/filters, but what's going on inside them. The old tank, the one you used to prep the filter, didn't have or produce the same amount of ammonia as the new tank, which has the active soil. 

I wouldn't say the 5 weeks was pointless, but maybe you could have got to the same point in just 1 or 2 weeks. Okay I take it back maybe it was pointless. Sorry. But regardless of how many weeks, you didn't challenge the old setup with enough ammonia to create and sustain enough bacteria to match the amount of ammonia in the new setup. 

The good news is that with both types of bacteria you need being present, the old filter should catch up to the new tank very quickly. I expect you'll see ammonia start to fall and nitrates climb pretty soon. You may not ever even see nitrites.  

[Galabar]

In my thread, I needed 10ml of ammonia for a 55 gallon tank (for the type of ammonia I was using):

When you were dosing with Dr Tim's, did you see a non-zero ammonia reading (before it went back to zero)?

 

Edited June 21, 2023 by Galabar

[Miranda Marie]

You didn't feed it enough to create a large enough bacteria colony to manage the higher ammonia content of the new tank. You have a *little* bacteria, but nowhere near enough to count as cycled.

So yeah, unfortunately, it was basically pointless. I hope the tank cycles quickly for you from this point on though! Good luck.

[Odd Duck]

Probably not pointless, but you may have had more action going on in substrate, on tank walls, from plants, etc, than you realized.  You probably needed to challenge the tank more in order to build/sustain more in the filter.  So you’re likely partway there and the filter should get up to speed faster than if you hadn’t been running it at all.

[Beardedbillygoat1975]

I would take a bit of filter media from your other tank and squeeze it into the Oase biomaster. As others have said I think you under seasoned the filter. It needed to be challenged and nows the time. 

[Andy's Fish Den]

When I set up a new tank and want to get the filter cycling, I squeeze some goodness out of a sponge filter or two in the tank, as well as ghost feed the tank until I add fish. I've never used any kind of starter bacteria or ammonia to cycle, and not had any problems with a tank cycling. A lot of times, the tank has only gotten set up a day or maybe two before I add the fish, and no issues.