Do I need to re cycle tank?

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Mw1234

Aquarium Advice Apprentice
Joined
Aug 31, 2021
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I had a previously well established tank, which housed my 8 yr old Cichlid. He died about 2 months ago and I have kept the tank running but haven’t been adding food or anything.
A week ago I took out all the old decorations and added lava rock and live plants.
Then yesterday I changed the substrate from gravel to sand, but kept some of the gravel as I made a little island out of it for the rocks and plants.
In the process of adding sand, I removed almost all of the tank water apart from 1 bucket worth which I had the plants in while I was doing the change.
I also changed from an in tank filter to a HOB but moved the sponge from the old filter to the new.
I want to buy fish this week but I’m just worried that because I have made so many changes plus the tank has received no food for 2 months.

Do you think I need to cycle the tank again before adding fish? Or can I just start adding fish food and see if the levels stay ok? If so, how many days should I wait before adding fish?
 
Your cycle may not have completely gone, but i dont think it will be fully established as strong as it was.

Do you need to cycle the tank before adding fish? Of course not. Many people do a fish in cycle. Its reasonably safe if done properly, especially if you have retained some of your cycle.

If you want to cycle before adding fish, then just follow a fishless cycle process. If you are dosing ammonia, then do this until you are cycling 2ppm ammonia into 0ppm nitrite and nitrate in 24 hours. If you are ghost feeding, then ghost feed until you are seeing no ammonia or nitrite. How long will this take? Could be days, could be weeks. No way to know until you give it a try. Depends on how much of your cycle you retained.
 
Thanks for the reply. So if I ghost feed, and my tank hasn’t retained much of my previous cycle, I should expect to see an ammonia spike?
 
Hi, so I tested my water before I added food and was getting ammonia 0, nitrite 0 and 5 nitrates.
A few days after adding the food I’m getting ammonia 0.25, nitrites 0, nitrates 5
Would this be considered a mini cycle? Not quite sure what I need to do? Or, am I fine because there was still the nitrate reading?
 
Have you been adding food daily? Or just a one off?

You will have some cycle. The ammonia from the food you added is being cycled out, but you have no idea how much ammonia is being produced or how quickly it is being cycled out. This is why i dont like ghost feeding.

Dosing ammonia and testing daily, you know how much ammonia is going in, and how quickly it is coming out. Or using a cocktail shrimp, you know that a steady stream of ammonia is going into the tank, and if you cant detect any ammonia and nitrite you know your cycle is processing it straight away.

0.25ppm ammonia is basically 0. This wont cause any harm to fish if you want to add some. Just monitor things and do water changes if you detect elevated ammonia or nitrite.
 
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