Siphon Problems

[DRH]

Hi All,

Been hovering around here for around a month, finally made an account. I've been sucked in to aquaponics... first through massive amounts of reading, and then finally deciding to construct a very small setup (would love to build any one of the incredible setups on here, but don't have the money or the time for now).

Anyway, over the past few weeks I've gotten my fish tank (~5 gallons) set up and cycled, went out and sprang for hydroton for grow media (only needed 10 liters of it for my small growbed, so it didn't burn too large of a hole in my pocket), and have been working on getting an affnan style bell siphon working.

Unfortunately, finding a wide selection of PVC in my area has been rather difficult, and shipping costs are prohibitive. I finally found a gardening store that had some parts, so I was able to construct my frankensiphon (I'm exaggerating, it isn't really that bad). It's a 50mm bell, 25mm stand pipe (very short in the pictures below), 25-20mm reducer, and 20mm elbows and other pipe parts.

I was able to order a tiny 6v pump from China which is supposedly rated at 35 GPH (which I thought would be sufficient given my small growbed), but it really does around 22 GPH.

The problem I'm having, is that the flow from the pump is not enough to get the siphon started (it works when I use the sink faucet to fill it up), and I was wondering if anyone might have some suggestions as to how I could jerry-rig my setup somehow to activate the siphon given the large pipe size and small pump flow.

Here are some pictures of the growbed & siphon:


Thanks in advance for all your input, this forum is great!