Backyard Aquaponics
A place to discuss aquaponics

I just hooked up my half barrel grow bed to my system as it cycles. I decided to put in a U bend siphon, but couldn't get it to siphon completely to the bottom when I had the overfill tube in place. I removed the overfill tube and replaced it with a short piece exit pvc that I had drilled 3 4mm holes into to act as a emergency drain (1 on each side, 1 on the bottom).
I plugged the pump in and it fills, but the emergency holes drain it so fast that the siphon never kicks in full force. The GB will fill up right to the bottom of the U bend and then equalizes there, which for water level is just perfect 2-3" below the cinder.
I let the pump run for a couple hours without a hitch, water level stayed right at the bottom of the U bend. I blocked up the drain and overfilled the GB, when I released it, the U siphon kicked in and I had twice as much water draining and it drained all the way to the bottom . It appears that the emergency drain holes is acting as my main drain and if it overflows, the U siphon kicks in as an emergency overflow and drains the bed completely. Opposite of what I had planned and designed.
I did some testing and my pump is pumping 150 gallon/hour. It takes 20 minutes to fill the GB to the bottom of the U siphon with the emergency holes draining. With just the emergency holes draining it takes almost 10 minutes to drain. When the U siphon kicks in, it drains in just under 3 minutes.
What would be best to do? dig up the drain and cover up 2 of the holes so it will flood and drain to the bottom using the siphon? Or let as is, flood the GB and drain slowly using the emergency holes?
It fills in 20 minutes, so if I let it pump for 30 minutes and an hour off, I would pump & filter 75 gallons of water or 75% of my 100 gallon FT per hour and half cycle. 16 cycles in a day would turnover my FT 12x per day. I plan to stock my FT lightly, I am more intested in Vegies than fish, so I want to lean toward vegi production. I know I'm a little short on the GB/FT ratio with only 25 gallon of GB media for 100 gallon FT, but I plan on adding 2 more GB when I find another barrel I can split in half bringing it to a more acceptable 75GB/100FT ratio.
BTW my FT has been cycling on its own for over 3 weeks now and I just got a nitrite/nitrate readings, so that signals the start of cycling right? pH still high though. Todays reading are pH 8.2, Ammonia 4, Nitrite 1, Nitrate 10 I am still struggling to get my pH down. Over the last 2 weeks I have squeezed in 10 mediums homegrown limes into my system and didn't do a thing, occasionally I'll get a 8.0 reading, but the next day will be back to 8.2. Should I be saving my limes for my Coronas and get someting a little stronger like vinegar or muratic acid?
Thoughts, ideas, suggestions?

Peace,
Cory

Sounds like your siphon might just be a touch too big for your little pump. Siphons have to be balanced with the inflow to the grow bed.

It also sounds like you could simply use timed flood and drain with your stand pipe with holes and then adjust the siphon parts to simply be a normal overflow. You say the bed drains in 10 minutes by the holes in the stand pipe. Heck, you could do half hour pump on and half hour pump off in that situation. Easy to get timers with 1/2 hour increments cheap. You would still get a good 20 minutes of dry time before the next pump cycle.

If you really want to get the siphon to work, you would definitely need to slow down or stop up those stand pipe drain holes. Normally siphons will stop with a little bit of water left in the beds since they tend to cause a vortex and suck air before all the water is completely out of the bed.

As to pH, there is probably something in your media or source water buffering the pH up so adding acid is only going to bring the pH down temporarily. Better off being patient since Aquaponics naturally will have the pH going down as the bacteria get around to using up carbon in their processes.