We cannot say, what single board you need to use. There are many boards, that are fitting to your requirements. You yourself have to choose.
Most of your listed boards use the same microcontroller (as Juraj wrote in his comment):
The Arduino Uno (doesn't matter where you buy it, it's the same) and all the boards with a 328 at the end use the Atmega238P. The Sparkfun Arduino Fio uses an Atmega32U4, which is different from the 328P, but not a very big jump (though it implements native USB support). These are all AVR based microcontrollers. The Particle Photon is not an Arduino. It uses an ARM processor and has wifi.
To choose from the big amount of boards on the market, you should look into your requirements:
- How many outputs do I need? Only simple digital outputs or also PWM? If the latter, how many individual PWM pins do I need?
- How many inputs do I need? Only digital or also analog?
- What extra devices do I need? Relays for motors/high loads? Special boards? And how do they need to be connected (what interfaces they use)?
- What interfaces do I need to the outside world? LCD Display + Buttons? Bluetooth? Wifi? Or nothing?
- How computationtime- and memory-consuming are the calculation tasks, that I need to perform (resources)?
- What environment will the project be in?
Based on the answers, you can choose a board, that fit's all the requirements and still leaves a bit headroom for further development. To help you I will write some examples for your project, that might be fitting for you.
Outputs: I guess your pumps are using mains power or similar (Be VERY carefully with mains power. It can easily kill you!). You need a relay to control these. It would be easiest to use a complete relay board, that includes all the needed extra circuitry. Then you just need to use one digital output pin per controlled pump, which results in 5 pins needed.
Inputs: This depends on what level sensors you have. If they have a digital signal (like a simple switch, that triggers, when it is covered by water), you just need to tie one digital input pin to each level sensor. With 2 level sensors per tank and 2 tanks we need 4 digital input pins for level sensing.
If the level sensors work with an analog voltage, you need to use 4 analog input pins. Their usage is a bit different, since their voltage has to be converted to a number value by the ADC (Analog Digital Converter) inside the microcontroller.
Interfaces: This is mostly up to you, since you didn't specify anything. You can just build the device with any outside interfaces, if you don't need them. Then you also can use a board without wifi. If you think, that adding wifi in the future would be a great idea, you can use a wifi capable board and just disabling wifi, until you need it. (Thinking a bit in the future, what future development might get interesting for this project)
Resources: Controlling motors (pumps are only motors for the microcontroller) based on some simple inputs is somewhat the standard task for a simple microcontroller. It doesn't need much computation power, neither much memory.
Environment: The temperature is not a problem for you. Basically all microcontrollers can operate in temperatures up to 80°C und down to -35°C (the exact values can be found in the datasheet of the corresponding microcontroller). The humidity is more of a problem. You need to build a water resistant casing for the electronics of your project, so that no water can get on the electronic parts. Also - to be sure - you should put one or two of these little silica bags into the casing, which sometimes come with electronic devices or such. The silica bags will bind the water in the air inside the casing and will keep the electronics even more dry.
So you need a simple microcontroller with 5 digital outputs and 4 inputs (digital or analog depending on your sensors), so in total 9 free fitting pins. An Uno or some of it's variants are fitting for this. If you want it smaller, that the Uno, you might want to use the Nano, which is the same as the Uno, just smaller. If you want wifi capabilities, you can go with an ESP variant like the NodeMCU.
This is just an example. There are many ways to build such a project, so there is no definitive answer. Any microcontroller, that fit's your requirements, is ok for the job.
