A fish-in cycle can happen for a number of reasons, a new tank and bad advice, a filter crash, a broken filter, a massive power cut. Whatever the reason you have a fish tank, and the filter microorganisms have died. If you’re not sure what the filter microorganisms do click here.

You will need a test kit, and a dechlorinator. That’s it unless you are using buffers.

You do not need bottled bacteria, you do not need ammonia lock, you do not need special filter pads. The aim is to get the hard work done now, and get a stable fish tank that will keep your fish healthy and happy for years to come.

Firstly if you suspect you have ammonia and nitrite and don’t have a test kit do 2 x 80% water changes now. There are issues that might be caused if the pH of your tank and tap are wildly different, but that’s outweighed by the risks of ammonia and nitrite. Now you’ve done that order a test kit, here is a link to some we recommend (yes we get some pennies if you buy via this link, it helps us pay the website bills) You will need ammonia, nitrite, nitrate, pH, KH and GH tests.

Next start testing at least once a day, if you get any ammonia or nitrite readings do a large water change and test again, if it’s not 0, do another change.

That’s it, yes it’s going to take time, but once your tank is set up and running you can cut back and do one or two changes a week and feel safe in the knowledge you are doing your best for your fish.

Things you can do to speed up the process.

Do you know anyone with an established tank? If you do, see if you can have a small amount of their established media.

Add live aquatic plants, not only will they use up the ammonia before it can hurt your fish, they will bring in microorganisms on their roots that will help seed your filter.

Cut down on feeding, fish are cold-blooded, which means they need far less food than a warm-blooded creature. Reduce feeding to every few days.