I'm new here, thought of sharing my DIY arduino based aquarium automation build..
The interface is through bluetooth. I can control brightness of 3 LED channels individually. The features include timer for lights, fans, co2. Theres temperature sensors for Room and Tank. The fans are dependent on temperature of tank. There's also a DIY feeder made with servo motor and 3d printed parts. Feeding time can be set for upto 2 times a day. Macro and Trace fertilizers are dosed automatically. The dosing time, days and volume can be set individually.
Some pics;
LEDs:

Dosing Pumps

PCB

This project was completed around 6 months ago and it has been working great without any major issues. Recently I made a dedicated android app for this project, sharing some pics of it as well..
The App:

Temperature Graph:

The app retrieves log of 5 days from the microcontroller and then plots it into a graph. It shows some interesting facts! The room temperature can fluctuate drastically in just one hour, while the tank temperature responds gradually over a period of 3 - 4 hours. During 23/12/17 to 25/12/17, I had kept the fan settings as to turn on at 7am and turn off at 11pm, also the threshold tank temperature at which the fan will actually turn on was kept at 27 deg. However as you can see the tank temperature never touched 27deg, so the fans never turned on. But since 26/12/17 i changed the threshold temperature to 24deg and as you can observe the tank temperature is maintained at 24deg during 7 am to 11 pm after which the fans are switched off and temperature rises to ambient room temp at night. At some point the difference in room and tank temp was 6 deg! Shows how effective a simple cooling fan can be... If i keep some realistic temperature threshold, say 28deg during summers, i hope the tank temperature to remain constant throughout day. The fans will automatically turn on and off every few minutes if deviation is observed..
And finally, the tank which does not bothers me much except for weekly trimming and water changes


Regards