I'm the guy that gave him a few. I had an overpopulation, added assassins and by the time I saw his post could only see a few babies on the glass.
To start growing some for my assassins, I got a 10 gallon and pulled any I saw into it. They are growing bigger. Eventually, they'll start breeding. If you're still having no luck by the end of April, hit me up again. I think I will have more and larger ones by then.
On a related note, if anyone needs assassins, I have too many.