Euryhaline shrimps are hardest to breed. But some people get it, specially amano shrimp. Maybe same method works with alpha. I remember a good link, Logemann brothers caridina japonica breeding guide, but I can't find it.
Just a quick update, I've had many berried females but absolutely zero larvae and i am still feeding them around 5 to 10 fish flakes every Sunday evening for food. I've noticed a lot of green algae and biofilm growing which is more the likely from the food and waste so I've decided to put in some more macro algae to suck up all the nutrients/nitrates. I put a ball in this tank when i first set it up and after a few days/week the whole ball had vanished! It didn't break up and I had no snails in the tank at the time so I want to see if the same thing happens again this time (maybe the shrimp are eating it). I have wedged it up in the thermometer away from the bottom of the tank to try and keep it away from the Alpha Opae ula's.
Here's the green algae and the macro algae.