The Bubble Magus Mini 70 is a great reactor, but not ideally suited to running pearls at all I'm afraid.
It's really important with bio pearls that the effluent is directed directly into the inlet of a skimmer.
Pearls work by building up layers of bacterial mulm on the surface which contains the nutrients you're trying to remove. The mulm comes off in clumps and needs to be skimmed out otherwise it just dissolves back into the water and is pointless.
The Mini 70 is great for carbon or rowaphos, but as it has no outlet, just spilling out of the top like it does, it's about the most unsuitable reactor there is to be honest. Great reactor, but I'd see if you can get something like a PhosBan reactor which has an outlet you can direct into a skimmer.