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Would 2 royals work in a 125g. I would obviously have to upgrade the cover but Im hoping it would work. Also would 2 BN work with them too. I love having them in there for algae.

Depends on the size of the Panaque. If they are relatively small, and there's plenty of suitable wood and hidey-places, they'll be fine. Eventually [probably years], however, a 125g will be too small for a single large Panaque, never mind two.

The bristlenoses will probably be ignored as long as they are significantly smaller than the Panaques. Make sure there are some small hidey-places the right size for the bristlenoses and too small for the Panaques, so that the bristlenoses are able to hide somewhere if they are threatened by the Panaques.

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Mats

Three royal Panaqs would be better than just two.
If two of your fish are relatively same size, they compete until either one heavily stressed. Three fish is a good number to reduce such a stressed condition which is very often seen in big Panaque spp. Moreover, fish tend to eat food more in group of three than just two somehow.
Good luck,