Raising ferm temp with hot water heater?

My basement has been about 60, and on Saturday I started a stout using Belgian yeast (wlp500). I don't have warmers or anything like that, so I just set it touching the hot water heater. It got a good start and is at 68-about what I want. The ambient temp in that spot is closer to 63. I really didn't want the yeast to crap out, and it looks like it's in the range...my only concern is that sometimes the HWH is warmer than it is at other times, and I don't want the fluctuation to mess anything up. I'm not overly concerned, given that it is not an official style (Belgian Imperial Stout)-but I was wondering if anyone had any thoughts.

Something as simple as a large cardboard box can hold in enough of the fermentation heat and stabilize the temperature.

By the way, there is a Belgian-Style Dark Strong Ale recognized under the BA guidelines.

Wort temperature during early fermentation will generally be 4-6F higher than your ambient temperature. So, if your ambient temp is around 63F this will place your wort temp right in the range you are looking for. As fermentation slows, the temperature will drop to within 2F of ambient but fermentation should still continue. If after 1-2 weeks you notice the gravity of your brew is still too high, you can warm it up again to reactivate the fermentation and finish out. If it were me, I wouldn't have ANYTHING touching the hot water heater...but rather place the carboy/bucket within a couple inches to acheive the desired temperature.

Thanks for the feedback...I feel better about it now that it's going, so I'll move it so that it's not touching. I was worried about a slow start, but hopefully all is good.