I have a 240 with a 1280 and 2 Aquaclear 110's. There are a few problems with the 2180. The priming pump sucks, it is cheaply made definitely not up to the usual Ehiem quality. The pump broke after about 3 months of use and the priming pump just plane didn't even work very well, before it broke. Also the water flow is fairly weak, even with 2 there wont be much current in your 240. My XP4's flow 2x more. Its not all bad though the heater works really well and seams real accurate, although if it ever stuck on it would cook the fish fast it can raise the temp in my 240 about 1 degree about every 3 minutes. It had no problem heating the tank to 88 degrees when I was treating for ICH although I had to be careful and heat the tank up in stages because it would have heated the tank from 78 to 88 about 1/2 hour. I have since figured a way to prime the filter easily but its still a big heavy pig to clean. My 400 gallon tank has two XP4's and FB900 fluidized bed filter and DIY heater module, it is so much easier to clean.
