Fish-In Cycle Complete?

[Greg_DS]

Well after 42 days doing my first cycle I've had 3 days of double 0's and rising Nitrates, can I assume I'm done??

 

[eaglesaquarium]

If the double zeros continue for a full week without a water change, then yes, you are complete.


Continue to test daily to be sure for another two weeks to ensure that things stay on track as they should. If you are looking to increase your stocking, don't add more than 50% of your current stock at once. When adding more fish, limit your feeding for the next few days and closely monitor all your fish and the water parameters. There might be a minicycle, if the stocking is increased too rapidly, but it won't last very long and a water change or two should get you through it without any casualties. Good job and welcome to the forum.

 

[Greg_DS]

Thanks for the welcome and advice, I don't plan on adding to the stock. will let everything stabilise first!!

 

[Juggler75]

As far as I'm aware with a fish in cycle you aren't cycled till you are consistently showing double zeros with your final stocklist as your filter will only cycle to suit the current stock. additions of stock will lead to further cycles, albeit short as the bacteria colonies need to expand rather than start from scratch.

 

[eaglesaquarium]

Juggler, that's not quite accurate. The tank is considered cycled when it achieves double zeros for a full week with your current stocking level. Whenever adding new fish, if done properly, the bacterial colony will grow to accomodate it, without a problem, as long as it is done properly.

People with an established colony can donate up to 1/3 of their media without a problem. Which means that the remainder of the bacteria can colonize the replacement material within 24 hours. So, increasing your stock in a fish-in cycle (which almost everyone has to do in one way or another, unless you immediately fully stock your tank after a fishless cycle) can be safely done, without a minicycle if you limit your additions, cut back on your feeding and monitor everything closely.

A fishless cycle is designed to create headroom for your filter, but unless you actually fully stock your tank, the bacteria die off and you are going to have to rebuild it when you add more fish. The key is to up the numbers slowly, no more than 50% of your current level should be added at once, and then they should be allowed to settle in and allow the colony to adjust for about two weeks or so before even considering upping the number again.


Personally, I went through a fishless cycle on a small tank. Then, I was given some fish and the filter for my large tank. I popped them all in together, but wanted to get the numbers properly established for each of my fish. I actually ended up DOUBLING the number of fish I was given by this move, and I never had ammonia or nitrite levels that exceeded 0.25ppm and mainly they stayed under that level. After two full weeks of monitoring closely, changing water (~30%) about every 2 or 3 days and limited feedings, my tank was fully cycled for that stock. I let them settle in for a while after that and slowly bumped the numbers up to my current levels. I did it one group at a time, and I haven't seen ammonia or nitrite at all since that initial stocking.

 

[Greg_DS]

Thanks for the advice, I'll continue to test for the next few days!!