Beautiful! I look forward to seeing how this tank progresses.
What really intrigues me is the background lighting on the tank. I don't see that done very often.
I like guppies too; I have some now. I don't keep them with my shrimp, since they go after the smaller ones.
How do you feel about the structural integrity of the tank without the rim?
It's actually not back lit which is cool because it saves me some electricity. I was planning on it but the light is so high it just looks like that with the regular light. I will back light it if the effect goes away after lowering the light (assuming I do so). The only thing that kind of sucks is my stand is about 4 inches further out than I would like to accommodate back lighting but if I don't need it, I can't easily move the stand because I had to shim it quite a bit.
I am very confident with the structural integrity of the tank. This one has been derimmed for at least 6 months. I have another 20 long with the top derimmed that has been going for almost 2 years at my girlfriends apartment. Many people have derimmed the entire tank. I have two reasons for not doing so. First, I never took any substrate out of this tank. Second, I was afraid it may end up looking worse with the bottom seems since they are pretty sloppy.
That said, would I do it again, probably not. It's a bunch of work. Getting the actual rim off is not the hard part. It's getting the silicone under it off. On my other 20 long, I did everything as best I could and it took me at least 10-15 hours total. On this, I have only done the front well and that took me 5 hours. I got most of it off the sides and back but it doesn't have a "finished" look to it.
Instead I would buy one that is already rimless. It's quite a bit more, especially if you are comparing it to the Petco $1 per gallon sale but only slightly more than x2 the regular retail of a 20 long. With the amount of work it takes, I would rather just spend the money and have it right than do a bunch of work and still have the sloppy seems on the side, and the bottom if you do the bottom. A member says where he got his here- Sam's 20 Long Rimless Tranquility