Well, dang, that's unfortunate. In the description, it says: " * Get precise, real-time data on your aquarium's temperature, pH, and TDS (Total Dissolved Solids) from one device. Fits tank under 1" wall thickness after removing screw."
Have you removed the screw? In the customer images/reviews, there are pics of it not fitting over the rim (but the screw is still in) and also pics of it fitting over a rim. Hopefully, your trim is under an inch wide and removing the screw is all you'll need
I removed the screw and was able to get it in the 40B. The rim on the 75g is too wide. Another problem with it, though. If you're using a lid, cover, or canopy on your tank, you won't be able to put it in the front. On my 40B, I'm going to have to put it in the back where I can cut the plastic heater strip. That will make it less useful as I'll have to make a concerted effort to check it as opposed to being able to check it as I go by. I'll probably put one on the 40B and one on the 20L.