Not sure where your location is....need more info. can you take a few pictures of your setup that is already done? and a few photo's of the equipment supplies that are part of your system. also will need some idea of what type of system you're building. In a greenhouse? outside ibc system or barrel system. is it a hobby or commercial setup. again pictures are worth a thousand words. everyone can add input with a few photos to get started.
I live in Oregon, my aquaponics system is based on the ibc chop system. I work a ton of hours, and juggle time for aquaponics like everything else in life. So post us some photos and let the community help get you back to building/growing.
I've looked at your photos and was wondering how big a pump you are using and if you were able to get the drain reinstalled in the grow bed yet.
it not I would knock out the bottom of a small bucket and wiggle it down around the drain pipe to get the media guard back down and then either hand remove or suction out the remaining rock, and reset the bell, I once used some hot glue to hold down a spot on a media guard, after the clay pellets soak the new ones should compact better. later I pulled out the glue blob.
can you post a few more photos.
your siphon issues my guess without seeing the amount of water going in and whats underneath. may be to small of a pump so your not getting enough incoming water to start siphon or fill your grow bed