Hello guys i dont know if it is the right place to aks my question . I have to do a project on an automatic aquarium .So my aquarium must have an alarm system in case of( for example if the water level is down or the temperature is to high or to low) anyway this alarm should to bleep and to flash when there is a problem in the system . So my question is which Arduino should i chose for my project ?
Thank You
Hi, if you use the search window in the top right hand corner of this screen and type in aquarium it may have the answers you require.
Tom.... 
That would depend a lot on what all you want the Arduino to do and how advanced you want the alarm system to be. If you are only looking to measure temperature (Temperature Sensor - Waterproof (DS18B20) - SEN-11050 - SparkFun Electronics, digital) and water level (Liquid Level Sensor - 8" - SEN-10221 - SparkFun Electronics, analog) and output a noise and light then you could really get away with probably any of the Arduino boards so long as it had those inputs available. I personally would recommend getting an Uno, but that's just because the price point is a good midway and it will allow you to use in future projects as well.
the mini pro is $3
http://www.ebay.com/itm/1PCS-PRO-Mini-ATMEGA328P-5V-16M-16MHZ-Board-Module-For-Arduino-Compatible-Nano-/360732394240?pt=LH_DefaultDomain_0&hash=item53fd538300
If not programmed via Arduino UNO:
http://www.ebay.com/itm/USB-Adapter-Arduino-Pro-Mini-Download-cable-PL2303-Replace-FT232-RS232-TTL-UART-/231108553831?pt=LH_DefaultDomain_0&hash=item35cf24ac67