Thanks for the help. Yes it's the dry purple rock from Caribsea.
I got the tank as a present along with the heater and filter etc. It's too late to go back, and I don't want to upset my wife or kids by returning everything. So we march onward with what we have. I do have an Octopus 2000 skimmer on the way. There's no space for a fish room or place to keep water stored for a top off system or stuff like that. I will go check out that inkbird, thanks for the tip.
NO no no, do not take it back.
Change of plan then. Go forward with the HOB equipment. Sump would be nice, but like you said, short on space.
You will really need to take your time. I suggest the BulkReefSupply 5 Min video series.
Cycling your tank. Sounds like dry rock, but adding a Bottle of bacteria will speed things up, but if you have the time, you could do it old school, and let the system populate itself.
Once you have cycled, keep the lights off, and add some fish, turning on lights to enjoy them briefly, like a couple of hours a day to try and keep the Algae under control. A Yellow Tang, and a Yellow Eye Tang would be good for Algae control, and also splash of color. A Lawn Mower Blenny, and maybe a six line Wrasse. You have 90G so a good size tank. Three months in, and you could start adding light and Corals, especially once you have the hang of nutrient control, and Alk & Ca under your belt.
You are limited on space so a QT (Quarantine Tank) might not be possible. Ideally a QT tank is a great idea for anything before it goes in your tank.
Read, read, and read some more.
Best of luck.