This Instructable will show you how to make a Aquarium Controller.

The Ferduino Aquarium Controller is the better code Open Source available today.
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Aquarium Control is free software: you can redistribute it and/or modifyit under the terms of the GNU General Public License as published bythe Free Software Foundation, either version 3 of the License, or(at your option) any later version.
EcoTech Marine Releases Development Kit for Third Party Aquarium Controllers
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#2 – Expandability: Choose a controller that lets you easily expand as your needs grow in the hobby. You may only have a 29 gallon nano tank now but, if you are like many in the hobby, sooner or later you will want a bigger tank, decide to grow SPS (and want to add a calcium reactor), or want to start monitoring the tank in the other room. You want to have the option to add new things to monitor like salinity, ORP, or Ph for instance. Expansion should also not be limited to just a few feet. For instance, I have a frag tank in my garage and my main system in my living room both on the same controller. And another important factor is choosing a controller where the manufacture is continually creating expansion modules that interact with the latest aquarium devices like flow pumps and LED lighting. It is not just you want to do today, but moreover that you don’t even know what you’ll want to do tomorrow. IOT Aquarium controller by roroid is licensed under the  license.
Photo provided by FlickrSoftware & Updates only on my next projekts - Aquarium Controller II + III + IV
Photo provided by FlickrJust a little over a month ago the Vertex Cerebra aquarium controllers entered the US…
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Reef Angel Aquarium Controller is the first open-source aquarium controller to offer the reefing hobbyist full control of hardware and software to accommodate their reefing needs.Spend more time enjoying your tank and less time testing your water. The Fishbit Monitor brings real-time water monitoring to your aquarium. Get notified immediately when something goes wrong. Pair it with the Fishbit Controller for instant automatic control of your equipment. Relax.Track parameters, set reminders, and so much more. Pair it with the Fishbit Monitor to track pH, temperature and salinity readings in real-time. Automate your aquarium using the Fishbit Controller. Prevent disasters before they happen and keep your fish and coral happy!

The APEX AquaController is an aquarium controller that you can use to monitor various parameters in your aquarium and control aquarium devices from anywhere. For example, say your temperature happens to go over 84F one day, with the Apex you can have it send you an alert via email or text message and you can also have the Apex turn off the heater! Crisis averted. No need to upgrade all of your devices, the Fishbit Controller gives your aquarium equipment the power of the internet. Get hands-off and tell your Fishbit Controller to turn the heater off if the water ever exceeds 79 degrees. All from your phone.I didn't really ever think I'd need or want to use one of these aquarium controllers but I must say that after seeing one in person along with all the functionality this unit provided changed my mind. Once you get everything set up and running it really is very simple to use. It is so nice to be able to pull up the app on my phone to see my current parameters. You can even hook up a camera to this system and it will show live video for you. I don't use the video portion of it... yet.Aqua is an aquarium controller I built using Modulo to monitor and automate my coral reef aquarium. It controls lights, pumps, temperature, and logs data to a server!“We are extremely excited about this development,” says Tim Marks, president of EcoTech Marine. “While thewave driver already provides extensive functionality right out of the box, this enables customers to integrate our market-leading flow technology with their lighting, dosing, pH and other systems. We look forward to enablingcustomers to be able to fully customize and control their pump using the aquarium controller of their choice.”