Backyard Aquaponics
A place to discuss aquaponics

Six months of procrastination and finally got this far. No fish yet but will probably add two Fan-Tail Goldfish this week.

Articles I've read about flood and drain systems tell me that the cycle should be between 15 and 30 minutes. The longest I can get it is seven minutes. If I turn down the flow into the grow bed any more the siphon does not start reliably. I think the solution is to reduce the diameter of horizontal drain pipe. See picture below. Even better might be adding a ball valve to that same horizontal section. With the valve I could take out the bell and stand pipe and stick my hand down into the media guard without emptying the bed. Or else I misunderstand the problem. What do you think?


But what is the harm if it drains every seven minutes? Does it affect the stress on the fish? By the way, filling the grow bed from the fish tank lowers the aquarium water level between 15 and 20%. Can't imagine the plants care and if the fish don't care either, then why should I?

Hi skillet, I'm not 100% certain but I imagine that 15 to 20% falling and rising water levels will stress the fish. If I had to come up with a way of stopping (or minimising the effect) I would consider a sump tank between the fish tank and the bed. The bed drains into the sump and the sump lets water back into the fish tank at the same rate or slightly more (never even a tiny bit less) than your pump is pumping it out. This way the sump rises (with the flood) and drains (until it's empty just before the next flood) and not your fish tank.
There are probably others with similar systems who can advise better but that's just something to think about in the meantime......

If you do try this approach the sump doesn't have to be directly above the fish tank it can be to one side so as to still allow access to the tank. But the sump does need to be empty before the next flood starts to fill it. If any water has not drained it will accumulate with each cycle and your fish tank level will decrease until either the tank is empty or the sump overflows.

good luck

Based on my experience the cycle time is not that important. What is important is that the water has enough oxygen that you don't get root rot (pumping the water is usually enough to get the oxygen you want mixed in). You should be able to leave your system with the short cycle times without any problems, I had a siphon system that turned over every 6 minutes and it worked just fine.

Another option that won't cause fluctuations in the fish tank and works well without a sump tank is to switch your system to Constant Flood. Basically you would be pumping continuously and the level in the fish tank and grow bed would be constant (usually an inch or two below the media surface in the grow bed). The continuous pumping aerates the water in this type of system. You just need to top up for any water that evaporates or is used by the plants.

One thing to watch out for in a setup like yours is having a fallen leaf block the outflow. You might want to put a lose fitting screen or cover on the media guard to prevent that.

It's the standpipe diameter in the siphon that determines the flow rate required into the GB and in turn the GB F&D rate. The larger the diameter of the standpipe, the higher the required flow rate into the GB and the faster the cycle times.

Going down just one pipe size can dramatically reduce the flow rate required and increase the cycle time. Just as an example, compared to 20mm, a 25mm standpipe requires nearly twice the flow rate into the GB and produces cycles time that are twice as quick.

For your siphon to be reliable, the standpipe diameter and the first 6-12 inches of horizontal return line should be the same the diameter. After those first few inches you can feed into a larger diameter return line, but not smaller. So to lengthen your F&D cycle times I would reduce the standpipe and horizontal, not just the horizontal.

F & D cycles that are too fast can cause turbidity in the water, as the water is moving too fast and draining too frequently to allow fines to settle in the GB, so they constantly circulate around and build up in the water. This problem is exacerbated if the water inlets into the bell are at the very base of it. I place the inlets about 30-40mm up the bell.

Thanks, everyone!

Reduced the standpipe and horizontal drain from 1/2 to 3/8. Discovered the whole drain was clogged with pieces of hydroton. Cleaned it out - twice - and now we're cooking with gas. F&D cycle is 20 minutes. GB fill barely more than a trickle but siphon starts reliably about 1 minute after drain begins.

Neatly drilled water inlets an inch or so above the bottom of the bell are a nifty idea I hadn't seen before and a big improvement over the crudely hacked notches at the bottom of mine. Thanks again Mr. Damage.

Scotty, you have been an enormous help, both here and in my intro thread in the new member's section; viewtopic.php?f=45&t=28861.

The idea is to add another grow bed, one shelf up. So maybe that one should be a constant flood so as not to increase volume fluctuations in the fish tank. You mentioned previously you have grown lettuce in both types successfully. Are some plants more suited to F&D; others to constant flood?

I don't know if Sarah and Maybelle, my future goldfish, will be able to keep up but I would like to have two grow beds plus a tomato bucket and a pepper bucket. Getting excited about this again.

Definitely a good idea to keep the fluctuations down if you can and Constant Flood will help with this. Might be tricky if you're running the beds off the same pump since one needs constant pumping and the other doesn't.

Every system is a bit different so I can't really tell you what will work for you plant wise. Just about anything you can grow has been grown in either type of system.

No worries!...

I don't know if I missed something, but I think maybe Scotty has just gotten turned around somewhere in the convo skilletlicker... Both Siphoned F&D and CF have the pump running 24/7.

I might be missing something here as usual. Is there any reason the constant flood bed couldn't, or shouldn't be continuously fed?


Got the rest of my life to experiment with it. For now it's romaine and red lettuce, spinach, basil, cilantro, thyme, and parsley.

Update on the Siphon Sagas: Three failures since my declaration of a final solution. Currently draining every 10 minutes.

On a happier note: Brought Sara and Maybelle home yesterday. They seem satisfied and enjoy playing in the grow bed drain... every single time.

You guys are right - Sorry, I was thinking Timed Flood and Drain instead of siphon fed flood and drain. Flood and Drain with Siphons and Constant Flood work fine together as long as you're running the pump all the time. You actually could run a siphon system on a timer since the bed drains (oxygen to the roots won't be a problem) but that's not normally done and I guess you'd have to call it Timed Flood and Drain then .




It's fun having the siphons in a system but you can always just switch it over to Constant Flood if they become an issue.

Cheers

I gave up. Pity mostly because Sara and Maybelle like to play in the turbulence but it just can't be trusted. Real bummer when it empties the grow bed and never shuts off.

Something changed in your system after your first comment about getting the siphon cycling every 20 mins. If the cycle time reduced from 20 mins down to 10 mins and it isn’t cutting off, so it’s keeping the GB drained, that suggests the water flow into the GB was increased and is too fast for the siphon.

Thanks for your interest and advice Mr. Damage. Things seem more random than they really are because my system is so tiny and so new and I am so inexperienced.
After posting this I think the there were failures of the cycle doesn't start variety. In response I turned up the flow a little but also made improvements to the snorkel tube on the bell siphon. Then there were instances of siphon not starting and BG overflow so turned flow down again; then a couple misdiagnosed overflows. While this is going on I'm also planting seeds. In such a small bed, pushing against the clay balls in one place causes them to raise in another. My inflow tube sort of lays on the top and is held in place with a twist tie attached to the top edge of the bed. There is never a full head of water coming out of the tube. It varies from a trickle to a little more than that. Pretty sure hydroton balls partially blocking the end of tube can affect the flow, certainly at least the appearance of the flow. And when making all these flow adjustments I'm eyeballing it; not measuring ounces per minute.

And then I started to worry that the system might not be properly cycled so ammonia and nitrite spikes may be on the horizon. If that were to happen I'd want as much water as possible and obviously, total capacity is a little higher with CF than F&D plus one smallish fish stressor is removed.

So I think it best to run it as a constant flood for a little while. Once the grow bed matures and the threat of spikes pass, I'll be a little more experienced and hopefully better prepared to take on the siphon question again.