I feel like your best bet is ESPHome and the ESP family of devices. Last time I checked you could get the parts for a project like this off Amazon (with spare parts) for under 20$.
homeassistant
Home Assistant is open source home automation that puts local control and privacy first. Powered by a worldwide community of tinkerers and DIY enthusiasts. Perfect to run on a Raspberry Pi or a local server. Available for free at home-assistant.io
I agree if your diy an esp32 and a dht11 could easily handle those duties.
I use one with 2 DHT11s and two DS18B20s to monitor my HVAC temps.
Wouldn't any off the shelf temperature+humidity sensor work? I use Sonoff and Aqara ones with Sonoff Zigbee coordinator and Zigbee2MQTT, both are somewhere around 15€ a pop, integrate painlessly and do the job. Aqara is a bit smaller and has air pressure sensor, too.
I agree with this, unless you paticularly want to do it yourself. You could even get a couple for redundancy for und
Sonoff SNZ02 for a small coin cell device, or Tuya if you want to use AAAs. (Tuya ones are a little cheaper too)
Edit: A bonus one if you also want a screen in the tank: Sonoff SNZB-02D.
I have some sensors on a hognose enclosure and I can say for sure stay away from INKBIRD stuff. It integrates poorly and fails on loss of internet connection.
I don’t have a good solution for the heatmats yet but I’m looking into integrating an aquarium controller I have laying around to manage that.
For hygrometers there are a ton, but you’re going to want to look for low power and probably zigbee. the majority of the sensors I’ve tried have been an annoyance to manage batteries but the zigbee ones seem better.
If you have a Bluetooth proxy setup you can get Switchbot devices pretty cheap. They have an outdoor temp/humidity sensor for ~$15. I bought a pack of 3 for $36.
Bluetooth proxy can easily be setup with esphome and a ~$10 esp32
Agreed, switchbot has been working for a while great in my hermit crab terrarium
Not sure what temp and humidity levels a terrarium is expected to have, but Shelly makes a good device for monitoring both - https://www.shelly.com/en/products/shop/shelly-h-and-t-white.
Or one with a screen (still smart) - https://www.shelly.com/en-us/products/shop/shelly-h-and-t-gen3-1/
We use the latter in our bedroom which triggers the power outlet to a humidifier if it gets too dry when we're sick.