New System Question

[venturajm]

Hello, I'm new to the forum, and would greatly appreciate help from any fellow Aquaponics DIYers.

I have my two 25 gallon grow beds set up above my 50 gallon tank, but I have a couple questions before I add any plumbing or growing material. I'm not sure what's the best way to link the grow beds to my tank. Should I try a flood and drain system with bell siphons? That's the way I'm leaning based on what I've read on this forum and elsewhere, but then that means that my 50 gallons grow beds will nearly entirely drain my 50 gallon fish tank. Right?

Once I add a water pump, the water in my fish tank will be nearly depleted before my grow beds fill up and then drain back into the tank. No fish would be able to survive, right?

Would love some advice on what I should do next. Would like to add my fish in the tank this week.

[davidstcldfl]

Hi venturajm ... ...welcome to the forum.

Your stand and containers don't look strong enough to support gravel...
I belive Oliver shared in, 'Aquaponics 101' , that hydrotron will displace %50 of your water. So even if you do use flood and drain, and both beds fill at the same time...you'll still have water in 1/2 of your fish tank.

Some folks are using expanded shale, which is cheaper. It can be found at 'some' fancier garden centers that deal with orchids. Also check your local concrete plants....they use it in light weight concrete. Try to get at least 1/2 inch size media (up to 3/4")

Looking forward to seeing some more pictures...

[venturajm]

Hi David,

Thanks for the response. I think what that means is that, if I have one pump filling both grow beds at the same time, my fish tank's water will decrease by around 25 gallons while they're filling. Will the fish be able to survive that fluctuation in the water level?

(Apologies if I'm asking questions that have already been answered on this forum.) Please just point me in the right direction. Thanks!

[keith_r]

you'll have a pretty large fluctuation, for flood and drain, consider adding a sump,which would be the lowest point.. pump from the sump to the growbeds, overflow them to the ft, overflow the ft to the sump..
or with no sump, use "constant flood" - start with the flood "level" about 1.5 to 2" below the surface, and seed.. after the seeds sprout, put a shorter standpipe in so that the water surface is about 4" below the media surface

[Oliver]

Remember that with media installed, your grow bed water levels will only go from a high of about 2 inches below the top of the grow bed and maybe as low as two inches above the bottom of the grow bed. Now subtract that 4 inches or so from the total height of the inside of the grow bed and the remainder is the height of the water change in the grow bed. That water is one half or less of the grow bed volume between those two extremes, depending on media type.

Now, for two grow beds, you can double that number of gallons as the most water that will be leaving your grow beds and returning to your fish tank at any one time.

With media installed and both grow beds drained, set your fish tank water level to a fairly high level. Turn your pump on, and if both grow bed inlets are set for the same inflow, then they both should fill at the same time, up to the point of beginning siphon. At that time, your fish tank water level will be the lowest it will be and once both grow beds finish siphoning, it will now be at its new highest level.

If you determine that those water marks are acceptable, then you are in business. If not, then you may want to consider adding more water or setting the lowest siphon point a little higher, or both.

We have been using your fish tank to grow bed ratio in our systems and have found that it is a good compromise.

Keep it simple.

Oliver

[venturajm]

This information is really helpful. Thank you all for your help. More pictures to come soon!

[Shas]

Try to get at least 1/2 inch size media (up to 3/4")

David, what's the idea behind using such large media?
I see 1/2 -to- 3/4-inch river gravel (river rock!)
recommended everywhere I look,
but I'm darned if I can figure out the reasoning behind it.

I come from a cattle ranch in Colorado
where we grew 800 acres of corn and alfalfa,
so I tend to think of plants growing in dirt.
Now, I understand that dirt is not going to provide
the aeration and penetration of solids that we need,
but why not something like 1/4 inch gravel?
We have lots of that around here (we call it 'pea gravel')
and I would think it would provide much more surface area
as well as allowing the solids to filter down
and plenty of air to circulate during the 'drain' cycle.
Plus, the seedlings might actually be able to grasp the bits
and the earthworms could perhaps move through it.

I assume there's some magical information I'm lacking.
Can you help me understand this?

Thanks

[keith_r]

i had a half barrel with stuff smaller than 1/2" and it tended to "clog" up a bit,, didn't get good water flow
larger media just doesn't clog up like smaller stuff

[alex281]

Try to get at least 1/2 inch size media (up to 3/4")

David, what's the idea behind using such large media?
I see 1/2 -to- 3/4-inch river gravel (river rock!)
recommended everywhere I look,
but I'm darned if I can figure out the reasoning behind it.

I come from a cattle ranch in Colorado
where we grew 800 acres of corn and alfalfa,
so I tend to think of plants growing in dirt.
Now, I understand that dirt is not going to provide
the aeration and penetration of solids that we need,
but why not something like 1/4 inch gravel?
We have lots of that around here (we call it 'pea gravel')
and I would think it would provide much more surface area
as well as allowing the solids to filter down
and plenty of air to circulate during the 'drain' cycle.
Plus, the seedlings might actually be able to grasp the bits
and the earthworms could perhaps move through it.

I assume there's some magical information I'm lacking.
Can you help me understand this?

Thanks

not sure if this is accurate but from the way i see it, the smaller pieces of pea gravel usually fit together closer and more snug then random shaped large pieces. id imagine it would actually take up more space and leave less room for oxygen/roots. just my .02$

[davidstcldfl]

David, what's the idea behind using such large media?
I see 1/2 -to- 3/4-inch river gravel (river rock!)
recommended everywhere I look,
but I'm darned if I can figure out the reasoning behind it.

Keith and Alex already said it.....the smaller stuff clogs quicker then the large stuff.
Shas, if your stocking density were on the light side, or if you had more media beds then the 'given' ratio recommends.... your 'pea gravel' should work

Here's what I experianced...
I was given some river rock. It was on the small size...around a half inch. I used it in some small media beds.

When I revamped my system, I moved the original media beds and rocks.... I rinsed them clean (with system water) before setting up the beds again.
I added a few more media beds and I used the larger river rock...about 3/4 of an inch.

The beds with the larger media seemed to take 'a lot' longer, for them to be as productive as the beds with the older/smaller media.
I have a few thoughts on this...

One, did the fact, that the older/smaller media, already having bacteria growing on it, make the difference ?

Two, the media beds were fed by a common header, with each bed having a tee, with a reducing branch with a ball valve.
The beds with the larger/newer media were the 1st ones to recieve the fish water....the older/smaller ones were the last to recieve. I wonder if 'more' fish waste passed by the 1st few sets of tees, and the last few beds recieved more fish solids ?

Three, the smaller media obviously collected more solids, so I would think those beds had more nutes available for the plants. (?) (all the beds had red wigglers)

Maybe it was a combo of all of the above....?