Please follow the below template, it will help us to help you!
Expected Behaviour:
To not use that much ram
Actual Behaviour:
Using 80% of ram and the RED button on the webpage is red
Debug Token:
gxln9s1egz
I could not find the expected HW to get a good experience, therefor I do not know if the Raspi Model B is sufficent to run Pi Hole without any major lags.
Your added block list contains about 2.6 million domains, so that puts your total domains on blocklist at about 2.718 million. On a Pi Zero with 512 MB RAM, this uses 89% of RAM.
With the default blocking mode you are using (NULL), each domain in gravity is stored twice. Once for the A record, again for the AAAA record. With 2.7 million domains in gravity, that takes a lot of memory.
You have several options.
Leave as is. You still have 20% RAM unused, and unused RAM is not doing anything.
Shift your blocking mode to NXDOMAIN. This will store each gravity list domain one time in RAM, and will free up some RAM.
Consider using alternate block lists. The original 7 lists block the vast majority of ads. The collection of Wally3K lists below is a good resource. All the ticked lists will get you about 600,000 blocked domains.
Use a Pi with more RAM. The later models (3, 3B+) have 1 GB RAM.
Even with a low-powered Pi, DNS resolution doesn't put much of a load on the device. It's a few hundred bytes at a time. All the actual traffic (the vast majority of your bandwidth) is not going through the Pi.
A Pi-B has the same processor (but a bit slower clock rate) as the Zero, and many users (including me) have very good success with a Zero serving a whole home. The web interface is slower than on a Pi-3B+, but the DNS performance is not noticeably different.