Fish Tanks and Grow Beds

[David C Ruhe]

Does anyone have any real good ideas on building tanks or beds. Preferably on a larger scale. I've been in hydroponics for awhile and would like to expand to aquaponics. I'm building a new greenhouse just for this operation.  Thanks for any good ideas.  Dave Ruhe  In north Florida. Also will need large amounts of growing media.

[TCLynx]

How large scale?  I've built a 700 gallon fish tank with a couple cattle panels and hardware to hold em in a circle, a chunk of pond liner a tarp and a length of that folded 1/4" blueboard insulation.  You could get a fitted PVC liner made for most any size tank to make it a little easier and avoid having folds down in your tank.

 

I don't recommend building lumber and liner beds in Florida as I've been replacing all mine with stock tanks because of termite damage.  The moist area between the lumber and the liner is far too attractive to them and sometimes they want a bit more water and create their own plumbing which to me was a leak!  Now this is far more of a problem if you are doing gravel bed aquaponics and there are way s to do liners for raft beds that may be more reasonable but I'm no longer advocating lumber/liner beds of any sort for gravel beds in termite territory.

 

So what sort of growing are you planning?  Raft or media bed?

 

Currently, on a dollars per gallon sort of arrangement, the two cheapest options for media filled grow beds I've found are 100 gallon stock tanks or if you find a good price on food grade IBC's then they are a good option too.

 

As for large amount of media, well I'm too cheap to go buying large amounts of any light weight media for myself but when I talk Large amounts I'm talking a dump truck load (like 6 ton or 600 gallons worth.)  Here in Central Florida the best priced appropriate media seems to be the 1/2" brown river rock from pebble junction or Florida natural stone which costs between $50-$60 a ton and then delivery was just under $100 from pebble junction and much less for me from the other place since they are close by, but I haven't gotten stone in a while it's probably gone up.  Now I don't know what the options are like up in your area of North Florida but make sure you tell them you can't use limestone since the cheapest pea gravel is normally limestone in this part of the world.

 

Now there are a few places you might be able to look for some bulk light weight choices but I don't think any are manufactured in Florida or south GA so the just the freight on a pallet of something will probably cost more than a whole dump truck load of quartz river pebbles.  So when you say large amounts of growing media, what do you mean?

[David Hart]

Hi David, Looks like your thinking of going media...? TCL already mentionrd the big draw back, on that here in FL....the cost of the media. That's one of the reasons I'm going with mostly rafts, commercially.

I don't know how much you've already read about or know (?) You may want to consider attending the commercial AP class comming up at Green Acres. They use (and teach)  the system that Friendly use's in HI. It would be nice to have a 'proven design' to go with

http://aquaponicscommunity.com/events/florida-friendly-aquaponics-1

[Marisa Dawson]

Okay, I'm ready to show all my ignorance here ~ LOL.  Summer's coming to a close, and I'm thinking I could buy some used above-ground pools pretty cheap (Craigslist here I come!).  I figure they'll already come with a pump, solids filter and whatnot for about $100-200 and are a lot larger than IBC's. Then we could customize them or add extra pumps for our gardens.  Any thoughts on this idea?  Does anyone know if the plastic liners from swimming pools leach chemicals that are toxic to fish?  I guess I'm going to find out ~ LOL.

[TCLynx]

Hay Marisa,

      Before you jump too quickly there, a swimming pool is often too large.  Remember that you can usually run a huge amount of plants on even a fairly small fish tank.  How much space do you have for this project?

 

Outdoors here I highly recommend at least 300 gallons of fish tank just for temperature stability but going a lot larger than that can sometimes run you into issues managing to filter enough of the water each hour to stay energy efficient.

 

And yes, some people have run into problems with pool liners killing fish.  This usually isn't as much of a problem with old pools but then again old pools are more likely to spring a leak.  Some people have repeatedly killed fish using cheap intex pools while other people have done ok with them.  I'm not sure how to tell which ones are going to give you a problem and which ones won't other than trial and error.  If you are worried about leaching that might introduce questionable chemicals into the food stream, well in that case you better look for food grade or potable water grade materials.

 

For fairly simple media based systems, I would recommend aiming for at least as much media bed volume as you have fish tank volume and you can go up to as much as twice as much media bed as fish tank or perhaps even more.  So, plan space accordingly.  If you go raft bed, you can have a huge amount of space devoted to plants compared to fish tank so please don't jump in on the deep end of the pool so to speak if you don't have a large amount of space to use.

[Marisa Dawson]

Thanks for the suggestions!  Not sure if I'm going to use space on a friend's 6 acre farm or my small suburban yard or someplace at the school, we will see.  So I'm not worried about space, more concerned about budget and recycling materials whenever I can.  How many full-grown tilapia can be safely raised in a 300 gallon tank?  Or an IBC?  And I still have to do research on raft beds, I just figured out how a swirl filter works - LOL.

 

[TCLynx]

What constitutes safely?  Some commercial operations stock tilapia very heavily.  But if you have backup power for the pumps or at least an air pump on battery backup, you could probably handle 100 tilapia in a 300 gallon tank but I would probably encourage reducing the numbers as they get big enough to eat.

 

That is of course assuming your water level doesn't have to fluctuate much to run the system.  I've currently have 100 blue gill in a 300 gallon stock tank and they seem to be doing well but they are not too big yet.  Water flows constantly and the pump is on battery backup power plus there is supplemental aeration.

 

Just a warning on the tilapia, if you have mixed gender tilapia in a tank with access to the bottom, when the water temp gets warm, you will have more tilapia than you were expecting since they breed alot!!!!!

[Marisa Dawson]

Thanks TC!  We just got back from Sarasota, my son goes to marine biology camp at the Mote Marine Laboratory every year.  They do a bunch of aquaculture there, growing sustainable sturgeon, caviar, etc.  School starts next week and I will be meeting with our robotics teams then, so I will be contacting you and some other AP farmers in the next couple of weeks regarding visits.

It is amazing to read all the info on these boards.  I am so impressed by the amount of time and info you and other members so generously share with us newbies.  I especially enjoy it when you reply to the same issues over and over again ~ LOL.  I am learning so much and I truly appreciate all your hard work in spreading the gospel of AP!

I love the tip about frequent breeding.  I heard somewhere that there is a growing market for fingerlings, so my kids may also explore that side of AP as well.  Is there an easy way to determine the gender of a tilapia?

[TCLynx]

There are ways to tell the gender of tilapia though I don't know how easy you would think it.  In an aquarium it was rather easy to tell the male and female adult blue tilapia apart but the smaller they are the harder it is to tell by any means and manual gender separation is prone to error.  Basically you pull a fish out of the water and swipe the genetle area with gentian violet and look to see which way the parts seem to look.  I would have to go look up the details again to be able to describe which is which.  Trick is doing this without hurting the fish, keeping it out of water too long and without dropping the fish to the ground or into the wrong tank in the process.

 

Often tilapia are already old enough to breed when some of them are still to small to accurately sort by gender which make things even trickier.

 

One way to keep tilapia in a mixed gender situation without excess breeding is to use cages that keep the fish from accessing the bottom of the tank.

[Jon Parr]

I love the tip about frequent breeding.  I heard somewhere that there is a growing market for fingerlings, so my kids may also explore that side of AP as well.  Is there an easy way to determine the gender of a tilapia?

Try this link for a picture of male and female tilapia. It's much easier to see if they are older of course. http://www.infobarrel.com/Tilapia_raising,_sex_identification_and_b...

For growout tanks I use 8' diameter by 18" deep wading pools at k-mart, $13 each in the off season. Filled 16" deep they hold 500 gallons. Flatten the ground, place 2)4' x 8' x 1" panels of rigid insulation down to make an 8' x 8' insulated pad ($10 each at home desperate), fill pool, and there you go. I get 55 gallon blue plastic barrels here in town for free, used to hold soy sauce originally, and I split them lengthwise to make 2) 2' x 3' growbeds each. Very tough, can handle the weight of rocks and the stress of bulkhead fittings ($2 each at hydro shop). I use 10 barrels (20 beds) for each wading pool, plus some vertical towers and nft trays.

[Jon Parr]

BTW, I use 3/4-1" river gravel, $60 per cubic yard delivered. One yard fills 4 barrels (8 beds), and I don't wash it. It's river gravel, folks! It is covered with silt, turns your water all cloudy, and settles in a few days. Fish don't mind it, and there are minerals in it. It drives me crazy to see people suggest that you wash the stuff until it flows clear. What a waste of water, time, and nutrients. You should, however, make sure that the gravel doesn't wreak havoc on your pH. Do this by sampling a bucket of each available kind of gravel your supply yard has, add an airstone and water, and testing pH of each for a week or two. If it is stable, available, and cheap, then it is decided. If you are sold on the sheer joy of working with hydroton or similar, and I share your joy believe me, then add a hydroton top layer to the beds where it will be appreciated (not the tomatoes that don't get touched for a year or two). I'm setting up some with filter fabric and then sand, to try my hand at root crops. We'll see how that works.

[TCLynx]

Before deciding to Not wash gravel, I would say inspect closely.  The 1/2" brown river rock which is a reasonably priced pH inert media in my location, has too much sand mixed into it for me to feel comfortable filling whole beds with it without rinsing.

If I were to fill one of my 100 gallon grow beds with this gravel without swishing the baskets of it in bins of water first, I would probably have 4-6" of sand filling the bottom of the beds after running for a while and that wet layer of dense media would likely become anaerobic eventually and I'm certain would mess with the proper functioning of siphons.

 

The size of the sifting of your local gravel will make a big difference.  I expect if I could get 3/4" of the same kind of rock I probably wouldn't need to rinse off the dust since most of the sand winds up in the smaller size stuff.  However doing the plant basket swish in the bins of water doesn't use nearly so much water as say spraying the gravel with the garden hose does and I also don't worry about making the water run clear, I'm really just swishing the sand out.

[Marisa Dawson]

Thanks Jon & TC for the advice.  School orientation was today, the kids are getting excited and I can't wait either!  Can't think of anything more fun than robots and fish!  LOL