Backyard Aquaponics
A place to discuss aquaponics

Dandi, even at a cost pf $1.50/fish... isn't that cheaper than buying fish at a store ... remembering your petrol cost as well???

Probably need to have some tilapia in a separate tank to breed and be able to collect fry since yes I'm sure the blue gill love t-fry and the larger tilapia fry and small tilapia fingerlings also love to eat smaller fry. I noticed that in the duckweed tank, as the older fry got larger, I was finding less and less small fry to move to the fish tanks.

I'm gonna try and remove all the fish from the duckweed tank before I put some adults back in to try breeding again to get my overwintering stock.

I'm hoping that this way, I can grow up the fry/fingerlings a bit October-April/May before putting them out in big tanks to grow out over summer and harvest by December. This gives me over a year of grow out so it isn't as important to have really warm water the entire time and it should be easier to keep a smaller tank warm in winter and the catfish will keep the outdoor systems ticking over during the cooler months.

I'm interested in extending this fish/watt idea. Trying to come up with the most energy efficient per fish methods we can. However, it might be unfair to use tilapia in such work since they are so bomb proof.

Rupe, $1.50 a fish not bad I guess, but I think I can do better.

The large outside system can produce 500. Here is a break down.

86.2¢ per fish is not to bad.

It appears my indoor system is driving the cost up a lot. However, if I produce fish and not just hold them for spring then it can be justified.

$3.105/fish

There is a huge advantage to using the simple outdoor system over trying to raise the indoors. .87¢ vs $3.11 Clearly raising fish over winter is expensive! The proportions of water and fish play a role here too.

Now Im not quite ready to give up raising fish because I need to keep some breeders. So I guess a breeding operation using a small tank over winter for 5 fish is going to be need. Then I can heat the tanks and add light during the last month before spring so that I have fingerlings started for the next year. The trouble Im having is getting the fish to a consistent size during a 7 or 8 month grow out time. I think its a combination of not having the correct size feed and having a mix of male and female fish. I really do not want to depend on being able to buy my fish each year.

Bluegill, if they will work would be something that is not limited to living outdoors 8 months a year. They grow half as fast, but twice as many could be stocked. Of course that's more working cleaning 1400 fish instead of 700

Another option might be pacu because they will reach eating size in 7 months, but I don't know how to breed them. Rupe, any info to share on breeding these?

TCL, I have not seen even a single fry. So either they quit breeding or they are eaten the second they are released.. At first the mothers would defend the fry until they could swim fast. Now I see no evidence of that...

Had a couple of good bookmarks, but I think they're on the archive disk... this is the only one I could find... http://library.enaca.org/AquacultureAsi ... apr-09.pdf

From memory.... wont spawn in aquaria or small tanks... need large ponds... scatter their eggs and will eat them...

Generally spawned (all at once) by hormone inducement... then the adults are removed once the eggs have been laid and fertilised...

What's the water temps been like in your water there Dan, that seems to have the biggest impact on tilapia breeding in my systems. Definitely if you are trying to grow out a consistent size harvest all at once, you probably will need to do all male stock for your grow out but I don't know how you feel about feeding your fry hormone laced food. I wasn't too keen on the idea so will have to just cage them and deal with some variation in size.

Now if your temps are up and there is breeding going on (which is likely, then the blue gill are getting some nice live food) that will account for a huge amount of the size variation since the females don't get to eat for the week or so they are holding eggs/fry and then if they breed again too soon after releasing the fry, they really are not eating enough to put on much size let alone the fact that the males are just naturally bigger. I've noticed that when netting the tilapia out of the duckweed tank, a few of the females spit out fry, and those females were looking really sunken in the bellies since they had a mouth full of eggs/fry for perhaps a week.

Now if you are really trying to raise them at a specific rate then yes, feeding the graduating sizes and protein % food could make a big difference but is it really worth having so much separate tanks/feeds etc?

I'm coming to the conclusion that tilapia raised in a BYAP set up (where they can be kept warm enough to survive the winter though not necessarily warm enough to grow out in 8 months) probably grow at a similar rate to many of the other aquaponic fish. I think I would rate my tilapia and catfish as growing at about the same rate though the catfish can easily get much bigger if kept a bit longer.

So perhaps instead of trying to use the indoor set up to keep the fish growing at peek speed, you might be able to scale it back such that you can just over winter a fair number of tilapia in there at a more affordable temperature. As soon as you let the temp drop much below 70 F the tilapia don't need nearly so much food/filtration/aeration etc. They are practically hibernating. Might work out actually better to collect some of the larger juveniles or small adult tilapia to over winter instead of the fry, since the fry really need to be warm and well fed to get a good start. Hum, too bad my indoor system isn't big really enough to support anything larger than fry.

So I take it you have blue gill and tilapia outside sharing the big pond? And then how are you currently utilizing your indoor systems?

The indoor systems is holding fry from this springs rash of breeding. Im pretty sure few of this years fry will reach eating size before the water gets to cold. Thats is why I am planning to bring them all inside; to give them a chance to mature.

Due to having only 8 months of usable weather and breeding not taking place until water reached high 80s there is not enough time to spawn and grow out fry in a single season. So it looks like I must get them to breed indoors at the end of winter so they are ready to go by spring. They just don't breed as well in a tank as in my small pond and when they do most of the fry get eaten.

My goal is to produce a minimum of 400 eatable fish each season. Getting 500 babies of similar age all at once could be a problem in the tanks. I need 500 for up to 20% die off; though my numbers have been nowhere near that high. Almost all deaths have been due to jumpers.

I am definitely coming to the conclusion that unless you are really in a tropical climate or can afford to heat the water to the mid 80s all the time, tilapia only grow about as fast as many of the other aquaculture fish. In my sub tropical waters, I think the catfish and tilapia are pretty evenly matched for growth rates though the catfish will get much bigger given more time.

I expect your could bring the electric costs for this system down quite a bit. And then if you allow the system to cool off a bit for a couple months you could save on feed and heating for a while too, probably reduce the pumping as well since tilapia in cool water won't eat and cool water holds more oxygen so won't need as much aeration either.
How many gallons in that system and how high do you need to lift the water?
Granted any changes might mean some cost of more energy efficient equipment.

$3.11/fish as a worst-case really doesn't sound all that bad to me. What's the average weight of the meat you get per fish after harvest?

At my local farmer's market, tilapia (farmed and wild) fillets are $6.99 / lb and live adult tilapia are $4.99 / lb.

Like TC mentioned, you can try for energy savings in various ways. Some ideas that occur to me:

You could put your add-o-mizer on a timer or on an oxygen meter-controlled switch.

You could allow for a daily fluctuation in temperature and reduce your heating cost.

You could try to super-insulate your tank.

You could build a rocket stove to heat your tank instead of the pellet stove and use free wood instead of buying pellets.

Most eating size tialpia are 600 grams. I think I was getting about 15% to 30% of that in meat. I would have to look back in this thread, but dont have the time just now.

If I forget the add-o-mizer and just use my packed column/trickel tower then I could use a much more efficient pump. I plan on testing this idea to see how much it improves the D.O. The water has to be lifted 6 to 7 feet because of how tall the aeration column is. There is 700 gallons of water and having a lot of fish requires some extra oxygen.

In other matters, my gravel is no longer draining fast enough to keep up with the siphon so I did away with it. I made a home made drain valve using what I had laying around: pvc, all-thread, a washing machine break, some 3 inch to 1.5 inch reducer, and a split racket ball. If I purchased everything this would have cost $50.

The washing machine break is powerful and powered by line voltage so it is connected to the pumps power line. No relays, no microprocessors, just simple and effective construction.

Valve made with split racket ball, washer same size as drain hole, nuts and all-thread


Washer and nut siliconed, just because I could


Valve fitting into pipe reducer


Inside the valve
[img]http://www.surveyingeducation.org/test/images/ValveInside.jpg[img]

Outside of valve


Valve in open/off position


Valve Closed when pump is on

Hum, very interesting!!!!! Yet another possibility for a low pressure automatic valve.

I have a car door actuator that might work instead of the washing machine break. Any idea what kind of amperage I'd need on a 12 vdc transformer to operate a car door actuator? If the actuator doesn't prove strong enough, I might have to look at the break idea.

Just curious, any reason you didn't simply do a stand pipe with some drain holes to replace the siphon since you are doing timed pumping anyway?

Why don't I use a stand pipe? I have s single 1.5 inch outlet from my grow bed and draining 1100 gallons of water through a weep hole in a drain pipe would take to long. I have so many fish in the pond I must cycle a minimum of every 45 minuets. Also, I prefer quick drains. Further, I feel the plants just do better.

Granted, you do have quite a huge bed to deal with. However, It kinda depends on the power of the pump/flow rate into the bed as to how slow the weep hole has to be. When testing out some timer operations lately I kept adding holes in the stand pipe till it took like 10-15 minutes to reach full flood and with that number of holes, the bed drains quite easily in under 45 minutes. If it takes the full 15 minutes just to flood a bed with a particular pump or if the pump is underpowered for a timer application, then it would be hard to get the bed to fill with more than the minimum weep holes.

However, your valve there is quite cool. I like it.

Just as a datapoint, I'm using 4th or 5th generation AP tilapia that were originally Miami Aquaculture rocky mountain white hybrids. They breed at 70*F and are still fine at 55-60*F.

Shocked the heck out of me when I drained my tank and found 30 or so fry in a tank that had been cold...

Where's Dan?

I hope he is okay.