Mt Gravatt High's system

[Starburster]

Hey guys,
We set up a system at Mt Gravatt High in April so we're still experimenting.
Murray sold us a 1000L tank and a grow bed so it's just a smaller version of the system he has. We have 20 barramundi that we bought from Sunshine Coast TAFE at about 300g each (because we need the system pretty much done and dusted by December for the 6 week break so we needed older fish). This helped to kickstart the nitrogen cycle pretty quickly although we've had to do a couple of partial water dumps since then. Seems to be pretty stable now though.
The only problem we're having with the barra is keeping the temp up for them. They work best at around 27 degrees so we've had to put 2 300w aquarium heaters in there (not the most economical, I know) as a temporary measure. Seems to be working though. We're looking at some kind of solar heating system but that's a bit of time and money away yet.
If anyone has any experience with barra can they tell me if they'll take to live food? We've tried worms but they won't take them. Maybe because they're captive bred and only recognise the pellets as food... Who knows?
Also, does anyone know what to do about aphids? They appear to have colonised our pak choi and I'm stuck as to what to do. Biological control using insects seems to be the best option, although I'm thinking it's maybe too cold right now. Any ideas?
If there are any other schools either doing or thinking about doing aquaponics, let me know. I would love to hear from you!
Cheers,
Brooke :cool:

Oops, meant to say that photos will be posted as soon as I remember to bring them home.

[Starburster]

Found some photos on my hard drive...
The grow bed drains directly into the sump tank and we buried pipes coming out of the sump tank back into the fish tank.
We need a second grow bed though, and there is enough room for one. Don't think the current grow bed is removing enough nutrients out of the water because our nutrient levels are still on the charts (ie not 0 yet).
Let me know what you think!
B145

146

147

[GaryD]

Hi Brooke,

It may take weeks (particularly in this weather) for your system to cycle properly so you'll have to persist with the daily water tests and water replacement until things come good.

The more grow beds you have, the greater the available area for beneficial bacteria to colonise.

I'd recommend that you get another one as soon as possible......particularly since, once your system cycles, you'll have plenty of nitrates with which to feed your plants.


The only problem we're having with the barra is keeping the temp up for them. They work best at around 27 degrees so we've had to put 2 300w aquarium heaters in there (not the most economical, I know) as a temporary measure.
You'll need to keep the temperature up or your Barramundi will stop eating. This will not only play havoc with your cycling efforts but they'll stop growing, too.

We're looking at some kind of solar heating system but that's a bit of time and money away yet.
There's already been some discussion about solar heating on the forum. See http://www.aquaponicshq.com/forums/showthread.php?t=77

If anyone has any experience with barra can they tell me if they'll take to live food? We've tried worms but they won't take them. Maybe because they're captive bred and only recognise the pellets as food...
It's quite likely that, if they're used to pellets that they'll be a bit indifferent to live food. Having said that, Barramundi are carnivores so it shouldn't take long for them to revert.

Also, does anyone know what to do about aphids? They appear to have colonised our pak choi and I'm stuck as to what to do. Biological control using insects seems to be the best option, although I'm thinking it's maybe too cold right now. Any ideas?

Try using a spray bottle and wash them off of the plants with water. Recent posts have mentioned using Seasol as a foliar spray for some things. I don't know if it works on Bok Choi but it's probably worth a try.


Gary

[Jonty]

Starbuster,

Usually when aphids are about, there are ants also. They often carry the aphids onto plants, protect them and milk the sweet substance they exhude.

Best bet is to get the garden hose out and give the plants a good hard spray. Should knock them off and kill them.

System looks great.

Regards
Jonty

[daniel]

Here is what I do for Aphids, Its a link from one of my sites. (Sorry for the self promo here)

http://www.whatcanonepersondo.com/blog/index.php?/archives/24-Tabasco-vs-Aphids.-Keep-bugs-off-your-Vegies..html

Basically use a Tabasco/water mix. Don’t know how long the chilly will stay in the water or if it will affect the fish in a smaller system.

Also, I have heard that you can buy live lady beetles, the natural predator of aphids. This may be an option.

[Starburster]

Thanks for the information, guys.
Daniel, I don't know if the tabasco will upset the fish (although it might add a nice flavour!) so I'm not prepared to risk that at the moment. The tabasco mix has detergent in it, does it not? I don't know how well the chilli will go with the fish but I know that the detergent won't
agree with them. What about a mix of garlic and water? Has anyone heard of that before?
I'm just leaving the system alone today because of the wild weather snap we've had in Brisbane. It's about 7 degrees in the greenhouse today, the water temp has dropped a couple of degrees so maybe the wind will knock the aphids off until we get time to try spraying them with seasol/the hose.
The tabasco mix has detergent in it, does it not? I don't know how well the chilli will go with the fish but I know that the detergent won;t agree with them.
Cheers, and have a great day!
B

[Murray]

Starbuster,
The Seasol spray will keep the bugs off, particularly leaf eating bugs. You will have to do it weekly. The Seasol will not hurt the fish at all.
It is not as effective on Aphids, but helps keep them from getting too bad.
There is a product by Yated called "Dispel" that is a Bio-insecticide. It's active ingredient is some kind of bacteria that gives leaf eating grubs and the like a bad case of the trots...so I understand...I am not a chemist. I have used it on Aphids once and it did appear get rid of them, but it might have been the Seasol.
The info provided by Yates says "Will not harm other insects, birds, fish or warm blooded animals"
It can be found in most hardware shops, garden shops and the like, and it is very inexpensive.
I feel the Seasol is your best beginning point.

I think I will give Daniels "Tobasco" brew a try, sounds like a good thing. I will try it with a small system I am building to see if it troubles the fish or not.

Murray

[njh]

As Jonty said, aphids are usually spread by ants, who will then defend those aphids against all other attack (I fought argentine ants for a few years). The best control, I've found, is to stop the ants. If your benches are raised on posts, ant tack gel is an effective barrier.

[Murray]

Good thought NJH, the ants are the key.
I used a mix of brewers yeast and honey, and spread it around my house some time back....ants all gone. Evidently the theory is that the ants eat the mix and when it gets into their little tummies the yeast gets moist and rapidly expands... boom....ants die......

Muzza

[daniel]

Thanks for the information, guys.
The tabasco mix has detergent in it, does it not? I don't know how well the chilli will go with the fish but I know that the detergent won't
agree with them.
B

I tend to use "green" detergents suitable for reed beds or grey water systems when using this mix. Now i know i am mixing technologies here, but from my understanding of reed beds, the plants use and consume the nutrients from the detergents in a similar manner to aquaponics systems using fish waste. http://frogs.org.au/frogwatch/greywater.php


I have a small reed system I am testing at the moment. It has fish/snails in the last stage. It receives a fair amount of detergents and they seem happy. Having said that, they are in the last stage of the system.

[Murray]

Daniel,
I may not be getting all this, but there would only be enough detergent to make the mixture "wet" .....as a wetting agent....? Is that right ? If so then there would only be a drop or to of detergent in a 1 ltr mix.....Is that right ?
Muzza

[daniel]

2 Drops actually, but only in about 250 ml. It is very diluted and isn’t necessarily applied all at the same time.

I am no expert, but I cant imagine this to be a problem, even in a small system.

[njh]

The problem with surfactants (detergents, soap etc) is that it stops the fish gills functioning. I don't know the dose, but I believe that if a surfactant is effective it doesn't matter whether it is reed bed friendly or not, it will have the same effect on the fish.

[daniel]

ahh ok. Didn’t know that. But here is my reasoning, please correct me if I am wrong. I thought that the grow beds would eventually help to absorb the detergents just like in a reed bed system. and because such small quantities where entering the system (as most of the spray stays on the leaves), then it wouldn’t be an issue. It certainly shouldn’t build up in the system over time as far as I can understand.

Are there any other alternatives to detergent as a wetting agent? Seasol maybe?  (it is the Tabasco seems to be the important ingredient)

I am not trying to force the issue, just trying to learn through experimentation. I am quite happy to be corrected.


.

[sillyoldfart]

Daniel I have often used garlic and oil sprays in my soil garden, and sprays made with milk which allows it to "stick" to the plant foliage.

Very good technique for powdery midew and other fungus attacks on things like cucumbers.

Perhaps try milk as your "wetting" agent.

[GaryD]

Hi,


It receives a fair amount of detergents and they seem happy.

Bear in mind that what kills the fish (or doesn't) isn't the only issue here.

Fish (or other aquatic organisms) may continue to live in very polluted water......but that doesn't necessarily mean that you can eat them safely.

Do you remember the Sydney Harbour pollution warnings of a few years ago.......and there's the ongoing Georges River oyster debacle every time it floods.

Gary

[Jimmie]

Just looking at your photos of the School System. Those fish are Barra ???? They are a good size, where did you get them ? How old are they and how many do you have in the tank ?
We have had some cold days and nights, how are the Barra standing up to it ?
Jim

[Starburster]

Hey Jim,
Yeah the fish are definitely barra. They were about 250g-300g when we got them at the start of May. Being a school we're limited with when we can start and finish the program each year since we don't want to be tied down to it for 6 weeks every Christmas. They were about 4 months old when we got them. By Christmas we hope to have them around 700g so we can harvest and shut the system down. We have 20 of them in the tank but the system is not running even remotely close to full capacity. The 20 fish are just to keep us running for this year.
We bought them from the Sunshine Coast TAFE at Nambour - they run a big aquaculture facility (both marine and freshwater) as part of the Cert 2, 3 and 4 programs in Aquaculture. I'm actually going to be doing the Cert 3 later this year because then I am able to run Cert2 as a subject for the students, with me teaching and the TAFE assessing them. It's a nice vocational education aspect to what we're doing. They were $12/kg so I think all up we paid around $70 in total.
The cold was a major issue last week. Our greenhouse isn't a greenhouse in the typical sense - it's a large cyclone fencing shed with green mesh on the sides, laserlite on the plant end and an opaque plastic sheet on the fish end. Consequently, the wind rips through the greenhouse because there are no walls. We did some improvisation on creating a windbreak last Wednesday (it was 6 degrees in the greenhouse) and we have polybatt insulation and black plastic wrapped around the tank to prevent heat loss. We also have a lid made from styrofoam, mdf and black plastic sheeting so we don't tend to lose a great deal of heat. We have 2 300w heaters in the tank at the moment and we're comfortably sitting at around 27 degrees. We had a big drop last week because of the wind, we went from 28 down to 23 overnight.
We built a recirculating heating system that we run for a few hours at a time if needs be, although we have only had to use it once, on Wednesday after the cold snap. Basically we run a small submersible pump from the tank into a large metal urn that heats the water and runs back into the tank. It works very slowly and chews a fair bit of electricity so it's not the most economical system to run. It'll probably be better in the summer when we're not using the aquarium heaters anymore. The fish seem okay, although a little sluggish in the cold.
Next year we'll probably experiment with silver or jade perch instead of barra just because they tend to cope with the cold a little better. We live an learn, huh? :rolleyes:
Cheers,
Brooke

[Jimmie]

The urn is a good stop-gap measure. A bit innovative I feel. The cold snap has taken everyone by surprise.
At the end of term 4 are you going to BBQ the fish ?
I imagine that your students are making measurements of the fish weight etc as the project goes onward as part of their science ? And the vegetables ?
What are the kinds of things you are trying to achieve by having an aquaponics system in a school ?
Jim

[Starburster]

When you work on a limiter budget, it pays to be innovative!
We're going to give the fish away after we've killed them for a donation to anyone who wants one. The money will go to getting us up and running in 2008 and pay for most of the consumables - water tests, food, fingerlings, seedling, etc. Although eventually seedlings will be propagated by the kids when we get access to the second greenhouse so we can set everything up.
The students haven't done any measurements of the fish as yet because there is an issue with animal ethics. Not an issue, just not official approval to handle them yet. We can keep them as long as we don't use them for tests or measurements. That will come through in August though. Until then, the students do the water testing every day (ammonia, nitrite, nitrate, pH, temperature) and measure out how much food they're fed. All this gets recorded and graphed at the end of each term. They also measure the plants every day and record the growth, which they're comparing to a small soil garden we have outside the greenhouse. When you do a direct comparison like that, it's easy to see why aquaponics is a much more viable option.
We use aquaponics for a number of purposes at school. While I teach science, I also have a geography background so it lends itself well to discussions about water conservation and catchments. We also use it as a basis for acids and bases and ecological relationships - predator/prey, symbiosis, etc. The aphids have been good for this because it's allowed us to explore how ants and aphids have a symbiotic relationship and what that means for both species.
Food chains and food webs have also been a hot topic - how the food that consumers eat gets converted back into nutrients for producers. Photosynthesis, the nitrogen cycle and energy pyramids are also topics we've covered. That's just with the grade 9's (phew!).
Our year 10s do a water quality investigation each year, where they test water samples from a variety of sources to get an understanding of how water quality is affected by a number of factors. They seem to enjoy using the aquaponics system as a basis for that investigation. It took a few of them a while to understand that anything we put in either system will end up in the other. Particularly pesticides on the plants or any salt in the tank water.
I'm in the process of writing a curriculum that schools can use before, during and after setting up a system. It's taking longer than expected but it's getting there. I promised Murray a copy as soon as it's finished - it's coming, I swear!
I hope that answers your questions, :). Feel free to ask me anything else you want to know!
Cheers,
Brooke.

[Murray]

Hi B,
Can you elaborate on the "animal ethics" issue. What are the parameters for that issue.
Sounds like everything is chugging along very well. I must make a trip up there soon and take a peek if that is ok.
It is a pity the system will have to be shut down over xmas. By then your system will be well settled in and well balanced I would think, and in the new school year you will have to start all over again.
I will house your fish for you for a month or three if that will help.
Murray

[Starburster]

Hey Murray,
The animal ethis issue is a complex one. Basically, any vertebrates that are housed in schools, whether it's for ornamental or experimental purposed, needs to be covered by an approved animal ethics statement. Basically, we need to submit a copy of what we do to the committee (who only meet every 3 months) and they will either approve or deny it. It's just to ensure that we're not being cruel to the animals, etc. It only applies to vertebrates though, so if you use yabbies in an aquaponics system, that's okay.
You may keep vertebrates, as long as you don't handle them, experiment with them, etc etc. Strictly ornamental. So at the moment, until we get approval, we can't handle the fish. If we do, it's a substantial fine (in the thousands of $), plus our project gets shut down. The next meeting is in mid-July so we should gain approval then, which will cover us for the next 5 years.

You're more than welcome to come up and see the system, just let me know when you're free and we'll arrange it. It's a good time at the moment because the kids aren't there for the next week, so it's quiet. I still go in a few times a week to check and feed. We do this on a rotational basis so no-one goes in more than 3 times in the 2 weeks and they're checked and fed every day.

At the end of the year we'll not shut the system down completely, just finish off with the barra. We're planning on putting a few large goldfish or koi in it just to keep it cycling. They'll get fed a few times, but apart from that, little maintenance will be required. That's the plan anyways.

Cheers,
B

[Murray]

I went up to the school on Monday to take a look at the system and it is going really well.
Sorry I missed you "B"
Attached is a pix of the grow bed. The tomatoes are going great, the zucchini bush has small flowers.
I like the look of the 20 Barra gliding around in the tank. I wish I had some of those.
Could not get a good pix of those as my digital camera is auto focus and tends to focus on the surface of the water.
Aquaponics, what a wonderful teaching tool !!!!
Muzza