I got one from eBay for like 3 bucks. A 60x loupe with an led light on it. You'll know for sure when you're close because those calyxes will swell to the shape of a pear shaped water droplet. You'll be surprised with the final 2 weeks of growth. Just watch the temps and take it easy on the feedings. Go feeding, plain water, plain water. You'll know if you're close by then. Good luck!