Backyard Aquaponics
A place to discuss aquaponics

Dave, I have to admit that I am electronically challenged, and certainly this box looks pretty home grown. The timer is analog and the dials get your cycles down to the second, although it takes a few adjustments (being analog). Probably overpriced for what it is, but my light timers were either flooding the main tank, or underfilling the grow beds, there was no inbetween.

The tilapia take anywhere from 6-8 months to get to plate size depending on the water temp, feeding frequency, water quality, and sexing. I do not recommend starting with fry because they are fragile and will not survive water fluxes. Fingerlings eat most anything you throw at them and tolerate changes better, but plan for average water temps of 80 degrees. Which is why I do not recommend starting any fish rotation in January.

Here in California, we will dip into the 30's at night, which gets the greenhouse down to 60's without heat supplement (I use alot of passive solar methods), and water temp dips to 70 degrees. Fish slow eating at this temp, become susceptible to disease, which is why I don't start a new batch until March/April. I just placed my last batch of fingerlings in the sump tank two weeks ago and will harvest the stock tank over the winter.

Can you get Tilapia in PA Dave?

oh, and Gary points out the other reason not to use the light timers, although they ran my .3 Horse Power submersible I did have a couple of times when I came home to find the floor flooded after the timer failed to engage, which is why I use a sump tank equal in volume to grow bed space.

My husband feels that it is ok to just keep the system going and not use a timer. What is the reason for timers?

Hey Joyce:
The sump pump is going through an accelerated "torture test" if it is coming on and off every 15 seconds 24 hours a day 365 days a year. With it being the bottom-most point in the system if it fails then how much of your water will be lost before the pumps draw air? I'm not trying to be dramatic, I'm just really worried about those beautiful fish!

That was my thought, but Jeff, my other half, feels the sump can keep up with it as that is what they are designed to do.

If you are running a continual flow (as is done with NFT) system, then timers aren't needed because the water is constantly cycling and plants are extracting nutrients as needed. For flood and drain, the duration and frequency of watering depnds on grow bed volume/space and (source)stock tank volume. Some people rely on the float switch to dictate the frequency and duration as it cycles with the tank water level, however you have to get the tank/bed volumes equal to the motion range of the float switch, which has always been hard for me to acccomplish with a reasonable degree or reliability. A good accurate timer eliminates the float switch dillemma all together and cycles water based on time, not water level. Much easier to work with IMHO. Now the question is NFT vs. Flood and Drain? Both have thier pros/cons.

Hope this helps

To me it seems excessive cycling, (twice per min) and as your sump tank is filled at the same rate you may seriously want to look at getting a bigger sump tank as Mike has stated Joyce. We don't want you to be showing a whoops later. Think of it in terms of what if the sump pump fails, then you will understand where we are in our thinking. I think. :book:

Here's how I interpret your system:

You have a submersible pump on a float switch in the main source/stock tank (the big blue one) that pumps water to all the grow beds at one time. It is activated by when the increased level from the sump tank sufficiently fills it?

The water, after being pumped to the grow beds then drains into the little blue sump where the sump is on a float switch and is cycling as water drains in. When all grow beds are sufficiently drained, the water level in the big blue tank should be high enough to start the whole cycle over again, is this correct?

Or, is the main pump always on?
Inquiring minds want to know Joyce!

She has said her sump fills aprox 3 times a min and she is on a slow trickle on her grow beds not a flood and drain. Would that not imply her main pump is always on?
Wanting to reduce the cycling of the sump pump I see three choices.
1. Place a timer on the main pump.
2. Get a bigger sump tank.
3. Divert some water flow from the beds into the fish tank, slowing down the time it takes to fill the present sump.
Joyce, put the coffee on we are all comming to Florida to see this in person!

Joyce, I was just in Florida this summer. Too bad i hadn't discovered this forum yet!!! John, you get the attention to detail award. I believe you are right....

Joyce and/or her better half have already dug the holes for the sump (no offense- but yet another reason not to put tanks in the ground), so a larger sump is out unless you want to dig more.

If raising your grow beds is an option, you can raise them high enough to drain via gravity back to main tank. Joyce I set my troughs on stands to raise them to drain over my large sump. Saw horses work fine. Other than that, you can just go until one of the pumps fails and redesign then.

Lord knows, and he does, how many pumps and configurations I went through to get to where I am today.

Re the timers: The HPM ones at bunnings (i think a picture was posted months ago) seem to be the standard for Pot growers, they are around the $20 mark and have contacts rated at 10A and they stand the test of time, switching highly inductive 2kw loads on and off once per day for months on end

I have boght smoe cheaper ones from bunnings for my aquapriums, but these "skip" time and on periods sometimes. I shouyld have brought them back, but lost my docket.

Coffee is always on guys, you are welcome any time.

John understood it. The pump in the blue tank is on all the time. The trickle in each growbed is slow, maybe not slow enough. I will be working on the timing in the morning. Even though each growbed does not seem to get alot of water, seem is the key, the flow at the end is almost as fast as the sump. The stock tank pumps 2000 gal per hr. the sump pumps 3100 gal per hr. That is why the sump has such a big splash when coming out. I will try to slow things down a bit, but not sure it will make much difference.

Do you have the volume of medium your water is going through Joyce?
And the rate your stock pump is actually working at, at it's head?

We'll find out easy enough with that information if you can divert flow on your pump.

Steve - I ended up buying an arlec timer today - one of the types with the on off bits built into the timer. It was $9 from Kmart. Reason I went for this in favour of the HPM (of which I already have several) is that I need to turn on on the half hour and off on the hour (am now going to do 30 minute flood cycle and 30 minute drain cycle). The HPM ones I have do not have enough on/off sticks to put into the timer for me to get this happenning over a full 24 hour period. The arlec one I bought will switch 48 times over 24 hours if wanted (which is just what I need to do). Hopefully it is reliable. Worst case scenario is that pump stays on (in which case water will overflow into top of standpipe and back to fish tank (with grow bed staying full) or pump will not turn on - so no water to the grow-bed. Provided it just skips a cycle or 2, this should not present life or death problems.