I have never tried anything like this, so im only making educated guesses really. But I dont think you really have to see in it to know its working. I think if you could just see the entrance to it, and have the patience to sit and watch, you would know if the loaches are going in and eating. If you really wanted to see in it, you might be able to find something clear besides pvc to use? The only thing i can think of besides pvc (with the same basic shape) would be a glass test tube. Or maybe a novelty type shot glass? I dont know, there are probably lots of things that will work. But again, I dont think you really have to see inside to know its working. For pvc I would just try 1/2" or 3/4", especially if they are really small. I dont know if they have to be able to turn around in it, or just back out, again im just making educated guesses. You dont have to do anything special to it before putting it in your tank. Maybe just wash wash of the dirt or dust that is more than likely on it. Im lazy, i probably wouldnt even do that. lol
I have really been wanting to try the Repashy for awhile now. I have always been intrigued by gel foods, and this seems to be a super high quality food. I havnt pulled the trigger on it yet though, mostly because I dont have a ton of fish right now, and the ones I do have already get a pretty good variety and they arent difficult to feed in the least. And my shell dwelling cichlids are breeding too much as it is, im afraid if i feed them any better they are going to explode the 10g they are in. haha
I agree with you though, if the seller wanted your money bad enough they would get back to you. Im the same way as you, if they dont get back to me I dont sweat it, there is always someone else willing to take it no problem. I think I know of a place that will ship to Canada, if you want the link let me know...
That is if you dont pop first. lol Early congrats on that one!