New Tank & Cycling Questions

[worstist]

Yah my question before was anyone experience the big nitrate drop like I did. It's weird because I tested it multiple times and it slowly built up 20, 40, 80, 160 than 20.

Last night i dosed 1 PPM of ammonia again to see if it would convert it.
I double checked the readings again today.

PH:8.2
Ammo:0
Nitrite:0
Nitrate:20

Should I keep dosing ammonia every few days to keep my bacteria up?

I rather not add a piece of live rock if its not necessary, the reason I chose all macro rock was to not get any pests, or anything I'm not aware of.

I think I'm going to add 5-7 Chromis to the tank and leave it for a month to make sure my bacteria levels are good.

Should I do a big water change to get my nitrate levels down? They are at 20 now.