I've read mixed review on these are bubbles in the seam. My tanks all setup now so I guess I will wait it out and see what happens. Most of the silicone is good on that seam so hopfully it doesn't blow out
Just my two cents. I would be watching this thing like a hawk and preparing to take the tank down to re-silicone it. I would not want to lose my live stock on a "wait and see" issue. Rather better to tackle this issue and fix it.
Only worry if the bubbles grow, daily photos then quickly change from one to the other in the camera or computer will show you the change or hopefully lack there of