Breeder Colonies

I have been reading about a breeder colony: in other words a separate tank in which to breed new fish. The website where I found the information, Tilapia Farming At Home, is a US based website, and the suggestion is that by producing hybrids from a male O. Hornorum and about half a dozen O. Mossambica females, you produce 98% male offspring, thus avoiding the problem of over-breeding in the fish tank. In this website, photographs indicate that the offspring are a reasonable size and shape!

I need to get a second and third opinion about this, as well as checking availability of these varieties of Tilapia - but it sounds like a plan!

System Design

I've been thinking a lot about how to design a system in a 4m x 3M Keder house. I am coming around to the idea from Murray Hallam, that perhaps a sump is a good idea, mainly from the point of view of relative levels. The fish tank could sit on the ground, and the grow beds could be fairly low (which I would prefer, for access to climbing plants) especially if the sump was sunk into the ground. It could be completely insulated to help maintain temperature, and the growbeds could be insulated too. Another plus is that much of the pipework could be run underground, which, especially if lagged, would also help to retain temperature.

I needed to find out how big the sump needs to be, so I asked Charlie Price about the medium/water ratio in a grow bed. (He said it's about 2/3 to 1/3) I have worked out that if I have five bath-tub growbeds, I would need a sump with a capacity of around 450 litres.

I have asked Murray Hallam if I would be able to use the sump as a breeder tank - which could solve the fish stock problems. I read that you can have a breeder tank for Tilapia, and if you have a male of one type (specified) and I think five females of a different type (specified), the offspring are 98% male, and it occurred to me that these could live in the sump!

Now I have to find a source for a 500 litre tank of the right shape, preferably without buying two IBCs!

How Safe is Aquaponics?

The recent e-coli scare in Europe (the scare, but not the infection, has spread to the USA) has pointed up the question of safety in vegetables.

Over a couple of years, in the States, a comparison between green vegetables purchased in grocery stores, and those grown aquaponically, showed that the latter were pathogen free – in other words, the aquaponically grown vegetables were 100% safe.

However, ironically, again in the USA, aquaponically grown food cannot qualify for a Food Safety Certificate. The reason for this is the book of rules, and specifically two parameters which cannot be complied with. The disqualifications arise because of the presence, first, of animals in the growing area, and second, of untreated manure in the growing area. The book of rules does not take into account the fact that manure from cold blooded animals cannot transmit these diseases.

In the UK we have the Soil Association, and here we come across a similar contradiction – food cannot be considered organic if it is not grown directly in, and harvested from, the soil. And yet most of us are aware of organic farmers who would not eat their own produce, because of the pesticides they are allowed to use, and which would certainly kill the fish!

Is it time to re-evaluate? Well, I guess that’s up to the Soil Association. But I confess to feeling that the current definition of ‘organic’ is out of date and therefore lacks credibility. If you are growing in soil, you can gain organic certification without improving the nutritional value of your produce, depending on how you treat your soil; and of course it does not preclude the possibility that the produce could transmit e-coli. If you are growing aquaponically, you cannot do anything which might damage your fish, and if the fish survive, I reckon I will too!

So I feel enthusiastic about the proposed Aquaponics Association in the USA, whose purpose will be to 'preach the gospel' of aquaponics and perhaps persuade the certification bodies to adjust their criteria. Of course, the US, particularly Hawaii, and Australia, are way ahead of the British in the field of aquaponics - but we must do our best to catch up.

Garlic Spray

I looked at my one tomato plant in my greenhouse today, and was surprised and annoyed to see signs of blight - so early in the season, and after so little rain. So I decided to try mixing a garlic spray. I used most of the very small garlic cloves from last year's harvest, mashed them with a pestle and mortar, and followed the instructions - halving the quantities. I still have over 2 litres of the stuff left, and the recipe says it must be used fresh! Also my house stinks of garlic!

Whether it will deal with the blight or not remains to be seen!

16th June: It Works! After removing a couple of slightly blighted leaves and spraying with the garlic, there have been no further signs of blight! Next question - can the liquid be frozen and keep its fungicidal properties?

Fish Stocking Levels

I have found a lot of very useful information at The Aquaponic Source. In particular, though, I was looking at fish stocking levels, and found an apparent difference between the advice from Murray Hallam and the advice from Sylvia Bernstein, so I emailed Sylvia to get some clarification. These two ‘aquaponistas’ bridge the gap between Australia and the US, and Sylvia explained that there is no difference in the two sets of advice, one being based on numbers and the other on weight. I watched Hallam’s video (the short version) again and realised that his ‘1 fish per 10 litres’ refers to fingerlings. Problem solved.

I have often noted that aquaponics is not a popular practice in UK. In my search for information, I have not found a UK centred aquaponics book. (perhaps Stirling University could look at filling this gap!) What I did find, last time I checked with Amazon UK, was ‘Aquaponic Gardening: A Step-By-Step Guide to Raising Vegetables and Fish Together’ by Sylvia Bernstein, and having browsed her website, The Aquaponic Source, extensively, I realised that this is probably the most useful book I could find on the subject although it is based on US practice. Sylvia was surprised when I told her I had ordered it as it doesn’t come out until October! But I have pre-ordered it and will have to be patient!

One reason I have for looking at stocking levels in particular is because I have seen a house where I may end up living, and there is slightly less floor space than I had hoped for. The situation would otherwise be pretty good but I have to work out how to fit in my aquaponics project – hence the calculations! But I am sure it can be done!

Update

I followed up the rhubarb pesticide question with the website where I found the recipe. This was the emailed response:

I would imagine that a high enough concentration of rhubarb leaf pesticide in a small volume of water could harm fish but in a garden-pond scenario with a small dose that there would be little risk. However, by avoiding spraying the pesticide into the water itself you will avoid any risk to the fish.

ecologica di Jonathan Radford

So I guess that used with care, it should be OK.

I have received the brochure and a sample from the Keder greenhouse people, CLM. They look like everything I could want, but the prices are high enough to contract the sphincter muscles! I shall have to downsize my expectations – or possibly live in one! But they look fabulous. Exactly what I need.

Pest Control!

The issue of pest control in organic gardening becomes even more important when considering aquaponics. Will the pest control used harm the fish? Will it make them inedible? What pests might harm both plants and fish?

Apparently snails and birds must both be kept away from the fish, as they may carry parasites which can also attack fish. Does that include slugs I wonder? What if you feed a slug off your lettuce to the fish?

I found a DIY aquaponics unit on Youtube where the legs of the grow-bed stand were stood in containers of water to avoid slugs climbing up. It seems to me that it would be wise to prevent access to the unit for slugs and snails, and under cover, birds should not be a problem.

There seem to be a number of pesticides which can be made from plant extracts, and the most widely spoken of is garlic, which is suggested by Murray Hallam in his DVD. Another is rhubarb leaf, and I am still trying to establish if this is harmful to fish. My new best email friend Charlie, at Aquaponics UK, also mentions elder, and chilli. I quote here his responses to my email query about the use of rhubarb.

I also notice frequent mention of soap spray – with the warning that it should be ‘soft soap’, e.g. washing-up liquid, not detergent. This seems to make life difficult for aphids, as well as enabling any pesticide to stay on the leaves.

Of course we should never forget that all this produce is to be eaten by US!

“Hi Tim,

I’m afraid I’m not sure (even though 6 years of my PhD research was focusing on aquatic ecotoxicology or replacements to organophosphate pesticides), i don’t have a scoody doo, I’m afraid.
i have made formulations with rhubarb and elder which both worked great, but i have only used them in soil... but I’d be very interested to hear how you get on, please keep my updated...

Garlic, and soap sprays are well proven options... and ones we use with good effect, but you make reference to a Keder house, so I’d suggest making sure they don't get in and if they do, then establish a healthy population of beneficials... “


“Yes, we've used garlic, chilli, and soap sprays and they have been fine, ultimately it’s a foliar treatment and providing the surface area of your growbeds, if media, is not wet, which it shouldn't be, then any active ingredient should volatilise before it’s an issue.. if indeed it would be in the first place, similarly with rafts.
I would think it would be fine, and next time I get a pest issue, I’ll definitely try it... and keep you posted too


best wishes
Charlie”