Get rid of the siphon and put a metering valve on it.
When it's set up correctly, you only need a few cups of media in the hopper. Mine works awesome. Also, make sure you have a dry system. Water separator is a must.
Mine is very similar to the one in this video. You can purchase one pre-made (not made from pipe) for around 50-60 bucks. Well worth it in my opinion.
That looks like it would work well. Having the supply right on the bottom like that is gravity fed. Leaving it a siphon and it has to work against gravity. Do you have yours like that? Does it work a lot better than the siphon?
