Going Nuts

[Dek1]

You are doing a fish in cycle as mentioned by @Essjay. It usually takes around 4-6 weeks for a tank to cycle and the filters to develop the good bacteria they need to keep ammonia and nitrite levels at 0ppm. Until then reduce feeding and do big daily water changes.

Reduce feeding to 2-3 times a week. Don't worry, the fish won't starve. After the filter has established you can feed the fish every day and do a 75% water change and gravel clean the substrate once a week.

In the mean time, do a 75% water change and gravel clean the substrate 4-8 hours after feeding. And do a 75% water change any day you have an ammonia or nitrite reading above 0ppm, or a nitrate reading above 20ppm.
Make sure any new water is free of chlorine/ chloramine before it's added to the tank.

Small water changes don't do anything to reduce nutrients.
If you replace 25% of the water, you leave 75% of the bad stuff behind.
If you replace 50% of the water, you leave 50% of the bad stuff behind.
If you replace 75% of the water, you leave 25% of the bad stuff behind.

Don't bother testing for nitrates until the tank has finished cycling. Nitrate test kits read nitrite as nitrate and give you a false reading.

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You can help speed up the cycling process by having the water temperature around 28-30C. Have lots of aeration/ surface turbulence to maximise oxygen levels in the water. Keep the pH close to 7.0.

You can add liquid filter bacteria supplements like the microbe lift you have. I recommend adding a double dose every day for a week, then pour the remaining contents into the tank. try to add the bacteria supplement near the filter intake so it gets drawn into the filter where it belongs. Add the bacteria supplement after doing a water change.

Thanks a mill some of the info I've been getting before I joined this forum was very contradictory. Learned more in half an hour than in 3 bloody weeks