Backyard Aquaponics
A place to discuss aquaponics

I am finally building my system, and can not make up my mind. I really do not have a good floorpan for an auto-syphon, So I need to choose between continuous flow, or using a timer. I am using a hot-tub tank & pump, so I have plenty of pump capacity, but it is expensive. Are there advantages to only filling the GB's once or twice per hour? Does continuous flow make it too wet for the plants? What other issues are there that I should think about (ie. plant selection) before making this decision.

I think the problem with continous flow is that water is not always distributed evenly, but there have been systems use that method with success. As far as filling grow beds goes, the more often you can move water across the bacteria the cleaner your water is going to be. So more is better as long as your plants tolerate it and with plenty of oxygen the plants will be fine. Which one advantage to flood and fill is that each cycle it pulls in fresh air into the root zone.

Here are a few of the points about some of those different methods.

With continuous flow (no auto siphons) distribution of the flow and associated clogging of distribution system become the biggest challenges. You want to wet a good portion of the media so that you can build a good bacteria colony. Plants can often do just fine with continuous flow so long as their roots can reach the flow and sections of dry gravel don't bother the plants too much but lots of dry gravel doesn't do your bacteria much good.

Continuous flow where the water is always deep is another matter and requires more aeration and could be too wet for some plants.

Continuous flow is often more appropriate when pump volume is small. It can also be easier on certain types of pumps to run all the time rather than starting/stopping all the time.

With the hot tub pump it sounds like you might be better off turning the pump on/off though you should probably add an additional source of aeration if you do that.

Perhaps if auto siphons are not appropriate to your situation, maybe a flush, flout, or header tank might help you in another way. Flush tanks can be found by looking up the barrel-ponics manual and flouts are being experimented with by a few on the forum but I've not heard much about them lately.

What type of floor plan do you have? This info might better help people here to offer meaningful advice. As with anything, there are always choices and favorites, pros and cons and many decisions will be bassed more on what you find to hand rather than perfect world situations.

I do know that lettuce can do just fine quite waterlogged but strawberries tend to rot in too wet situations.

Thanks for such quick responces. I have two primary GB's each 12'X2'X12". I have one 30-40 gallon sump tank (mainly used to preserve water level in stock tank) and two stock tanks, one 150 Gallon's, and the other 300 gallon's, for a total of 500 gallon stock/sump tank. For the time being, I am only hooking up the smaller tank, so I can get the kinks out of the system before bring the other system online. I bring the water from the stock tank to one end of the GB through a float valve (to ensure that the GB does not overflow and to control the rate of flow) and have a drain at the other end (with flow control valve to regulate how quickly it drains). It drains into the sump tank (plastic barrel) which has gravity flow lines into the stock tank through a float valve. System is driven by a 1/2 HP pool/hot-tub pump, which has flow restricters. The line going to GB gets all the volume it needs, with the remainder being recirculated back into the stock tank. The system has a filter that I can run the water through to remove solids, or I can simply circulate bypassing the filter. I haven't taken any pictures yet, but I hope this gives you an idea.