This looks like a strategic error based on the desire to get bigger or address a financial objective rather than on the strategic need or benefit of combination. The majority of the synergy appears to be in the R&D, which doesn't appear to be a valid enough reason for 2 very different businesses to merge. It's more likely this will backfire. Competitors to Neptune (makers of controllers, pumps, lights, powerheads, dosers, etc.) won't want to sell through BRS, because selling through BRS strengthens Neptune. And competitors to BRS won't want to carry Neptune, because doing so strengthens BRS. Kind of how Pepsi lost out on sales to other fast food chains by merging with Pizza Hut. On top of all that, they've now destroyed part of the BRS brand strength by casting doubt on their perceived objectiveness in product testing and rating. Yes, both Neptune and BRS are dominant right now and likely won't see short term losses, but more competition is coming, and they just made it easier for their competitors to grab market share in the long run. It's a shame, because I like what both companies have had to offer up to this point as separate businesses.
This remains to be seen. As long BRS Customer Service stays good, they will have customers.
If those makers don't sell on BRS, they will be missing out on a big chunk of market.
This Saltwater hobby is already small enough (compared to other hobbies), I don't think those makers can afford to take their product out from BRS.