Well, I'm kind of a rookie as well, but I got my bell siphon to work. Did you put the air bleeder tube on it? Also did you scolope the bottom of the 2" outer sleeve to allow the water to rush in?
I also have a 275 Gal. tank which I buried and have stocked with 20 Catfish and 2 Koi. I have pea gravel as my planting media. and have 8 half barrels which will be running bell siphons. Currently 4 are being flooded via a 7' high flood barrel system. I use about 10Gal. per barrel, per flood.
Would be interested in what you are doing as well.
p.s. My cell number is 512.587.0328 and you can rech mea just about anytimes as I'm retired.
I had a similar problem I put an elbow at the bottom of the sand pipe this restricts the flow of water enough to start the siphon. Make sure the elbow is above the waterline. Once I did this no more problems with it starting did have problems with it stopping but this was solved by creating a larger intake it now empties in 2 min. good luck