Stocking a 55 gallon

So as some of you know I had a bizarre nitrite spike and it killed a few of my favorite fish. With this being the case my 55 is now essentially empty with the exception of 6 Sword Tails and 7 Cories (this is a separate issue being resolved now). Tank is old and established.

I have a Rainbow Cichlid at about 4 inches that will be going back into the tank in time. Any suggestions as to what you would stock?

Addionally, I'll be upgrading to a 120 or larger come fall, so juvenille fish that get larger aren't a huge problem long term, but of course I don't want to over stock in the meantime.

I'd like to get a Threadfin Acara, Jurupuri and possibly a Firemouth, but have also been looking at Daemons, Blue Acara, maybe a Gold Severum... I don't know its sort of a blank slate at the moment. I'm researching different fish, I'm not entirely familiar with the last two, but I believe they'd mix ok.

Also, my tank has now read 0 ammonia and 0 nitrite for 2 days now. How long should I wait before slowly restocking the tank? A week? Less? More?

Thanks!

Nitrite reappeared in the tank again last night after work. Went a day without doing a water change and it was back at .50

Left it as is and used Prime to detoxify. Want to check it after work today again and see if it continued to rise or if it somehow balances out on its own. This is so frustrating. Anyhow, obviously adding any new fish is completely on hold for now but I'm just trying to gather some thoughts and research what I may want to do once the tank's water parameters are healthy again

Fishfriend1 said:

I've suggested this before, but I'll to it again: Don't use Prime to detoxify. Let the tank detoxify itself so that you can actually know what your cycle is over and that you aren't simply putting a band-aid on it to prevent a crash.

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Yes I know, however Prime only converts the ammonia/nitrite to non-toxic form which the bacteria still feed on, and it will still show up on the water tests which will indicate how far along the cycle is.

Anyhow, it seems to be under control now. I think I've figured out why this happened.