Need experienced advice new 30L to hatch eggs

[Pineapples]

Hi I've just purchased my 4th tank and I'm experiencing something strange. I was wondering if anyone could help.

120L brackish SG 1.005 varies a little. 5 bumblebee Gobies

This is my first problem:

Ammonia test always goes cloudy but still yellow

Nitrites 0

Ph 8.2

Temp 28-29

KH 5-6

So do I need to purchase a salt water ammonia test kit for brackish?

Second problem:

Yesterday I purchased a 30L tank to put the goby shell inc eggs into. (To save my trying to catch the fry before they get eaten)

Now I filled is 70% with brackish water from the 120L and topped the rest up from the tap. Using prime and easy life filter fluid medium.

I took the submersible filter out of the 120L (still have a hob and a sponge filter in there) and put it in the 30L I also put another sponge filter in the 30L

A few hours later I test it just to be sure

Ammonia still cloudy but yellow

Nitrite .50ppm

Ph dropped to 8.0

Temp 28

KH 4

So can someone please tell me what to do about these nitrites?

I was planning to put the shell with the eggs and the male bumblebee goby in there tomorrow or the next day so I need a quick fix!

Would purigen work?

Or is there some type of bacteria culture you can buy to kickstart it?

I understand the problem is that it's not cycled properly but I thought using the filters from the cycled tank would fix that.

Any input or suggestions would be greatly appreciated.

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