The current issue is that clipping aquariums together can cause them to be deleted.

The potential solution that they might implement sometime down the line (not with the patch) could cause all furnishings that are overlapping/clipping to be deleted. I sincerely doubt they'd actually go through with this fix, but even if they do, I'm sure they'll give some warning. For the time being, we don't need to worry about most furnishings clipping, but after the patch hits do not clip aquariums through each other.