The way we do it in theater, is to hide regular lighting instruments as near to the purported light source as we can. Gobos (aka projected patterns) can help a lot with the realism. I use this method in 3d as well as I find it more intuitive and easier to get specific effects from. If you mean to do this in Anything Glows, however, it can probably be done. Unfortunately Aglows is limited to, I think it is, 200%. Then there is the glow channel of the object, which since that affects what the object itself looks like can't be set too high. Lastly, I do believe Aglows uses the Indirect Light model and slider. Again, funny things can happen with Indirect light set to several hundred percent -- but it is the only setting in this chain that you can crank up to extreme values. You do have a last problem; both your fish tank and fireplace are set into one wall. Meaning they backlight anything in the foreground, and can't even illuminate the wall they are set into. So for this scene, particularly, I think a non-realistic, theatrical, approach may work better for you. You could add in a little subtle front fill without having to excuse it. And besides...this way you can also make sure there are nice detailed caustics coming out of that fish tank light!