Originally Posted by StarlightGenesis
I tried fly predators and they didn't work for me, I have no idea why.
There can be lots of reasons.
For starters, they do not instantly make a fly infested place not have flies. If that was the affect you were going for they do not do that.
If you were still using chemical fly sprays you could have been killing off your predators.
If you were using any feed through fly killers that too will kill your predators.
If you have another farm close by that does not use predators, that can make the predators less affective because the neighbors flies can come visit your place.
I personally have had very good luck with fly predators.
I also have a biting fly trap
which does a good job at lowering the amount of nasty green heads.