A reef flats is a rich environment, multiple species of crab, hermit, snails, sea urchin, sea stars, minnows, baitfish….
For a same crab it could be a blue one one the reef but in the grass patch of the reef, he will be greenish and on the sand it will be white covered with dark spot on it to fit perfectly with the sand around him…..
Bones have such differents source of food to feed on that if you drop any bonefish fly in a perfect way, they will took it.
On the other hand, I’ve clearly seen throught those months here in Guadeloupe that they are also more keen on some pattern. Sometimes after switching flies from flies I come to a pattern that turn them in crazy grabber, one is “runing” 10 feet to took the flie, others fights each other to be the first to took it or other kind of “plop, stri.., fish on!” patterns.
This bring me to the “fly of the day” theory.
it goes in three different way :
1 – it’s look like a prey they haven’t feed/found for a long time and once they see it they are like “ho my god I can’t belive it, I love eat those one…I want it…I want it…Shromp…wizzzzzzzzzzz make your reel”
2 – The pattern fits what are mostly feed on this day
3 – The pattern look like a rare and juicy/testy prey that live on the reef and hard to find for them so once you show them the pattern it goes like in the first point.
I strongly belive that from day to day they will feed on this crab tuesday and wednesday it’s an other or a different specie. Also never forget that a bonefish is a pig flats and will eat anything he will found an easy prey.
As the bottom is mostly hard on a reef they will shomp a crab, go 5-10-20 and even 60 feet, shomp a hermit etc. It’s also a part of the “fly of the day” theory. If they wanted, they could stop each feet all day long to feed, the bottom is crowded of bones prey. So why do they moved so much….in my opinion they are looking for some specific prey. As you alreday doubt, it is complicated by specific grass preys and sand ones….each different bottom patch got his own part of feeding pattern. On a reef flat you will have all that, reef, sand, grass, coral.
Just a quick word about permit, if you found a mixed bone/permit school, make the cast and strip as for bonefish it could be the only time a permit will think as a jack and grab the flie before the bonefish. In this case you want a flie that work for bones as permit…in my book a “shrimp or mantis shrimp” pattern.