Just leak testing the new tank and I’ve noticed these air bubbles in the silicone seam, these are near the bottom and there’s one two on the other side that’s about 2” long each but quite thin and very hard to photograph to get the idea of what they look like


That's not what you want when you go custom! We have had a number of tanks made over here with nothing to complain about, sadly someone is always unlucky! 
Well, since I am based in Scotland, we have used a local chap up here in 'Bonnybridge'. He is mostly building for commercial aquariums, but he have made exactly what we needed for both frag tanks and quarantine setups!

