High nitrites in cycle

[Tank Mate]

I've been keeping fish for coming up to a year but I've never had to run a cycle as my first tank was second hand and already matured.

However, I recently bought my second tank (Fluval Edge 46l) and thought I'd chuck the bio media in the rear sump of my main tank (AquaNano 40). For more context, I've also god around 500g of Fluval Bio Rings in the rear sump in addition to the stock media.

I left the new media in the established tank for around a week and last Saturday transferred it back to the Edge along with some of the established bio rings. I also squeezed some of the sponges into the Fluval to get as much biofilm as possible into the system.

After letting the tank clear, I then added my three juvenile mollies (almost 2 months old) into the Edge and they loved the space. However, I tested the water the following morning and found high nitrite readings of what looks like 2ppm - 5ppm (it's hard to tell with the API liquid kit).

I immediately did a 25% water change to being the nitrites down and returned the mollies to the main tank just in case. The nitrites dropped slightly but they're now at the lower end of the 2ppm - 5ppm spectrum. For the record, ammonia is reading 0 or trace.

My question now is what do I do? My tap water naturally has a high nitrate content so I can't monitor whether the nitrite is converting other than checking if it's gone down. Do I do more water changes? Let it lie? Feed the empty tank for more ammonia?

Appreciate your thoughts. Picture of the tank for reference!

[Tank Mate]

Scratch the ammonia reading. Thought I'd do another test and it's at 0.5ppm

[Tank Mate]

Another update: ammonia around 1ppm but nitrites have dropped to 0. Any ideas??

[ZxC]

Likely the tank is just not cycled, and does not have enough bacteria to support the mollies. Add an ammonia source and test until cycled - ammonia 0, nitrite 0, nitrate whatever your tap is plus a little. Then add a few or two and see what happens.

[Tank Mate]

Mollies went out morning after they went in.

Tank kick started cycle with established media. I've still got 1ppm ammonia but nitrites have disappeared overnight

[ZxC]

Originally Posted by Tank Mate

Mollies went out morning after they went in.

Tank kick started cycle with established media. I've still got 1ppm ammonia but nitrites have disappeared overnight

The bacteria population is likely adjusting to the sources of energy you have. Lots of nitrites will cause an increase in the bacteria that utilize nitrite, this will have no effect on ammonia. Unless there is a balance of bacteria types, your reading will likely jump around. A good, stable source of ammonia will produce a good stable source of nitrites which will produce a good stable source of nitrates which you remove with water changes. you likely have a higher count of nitrite utilizing bacteria opposed to bacteria that utilize ammonia, resulting in nitrite drop and little to no ammonia drop.