Larviculture newsletter < Year 2005 < Issue 230

ELECTRONICAL LARVICULTURE NEWSLETTER ISSUE 230
15 October 2005

1. CONCRETE TANKS IN LARVICULTURE
2. AQUALAB TRAINING COURSE "QUALITY OF FISH PRODUCTS"
3. QUALITY OF TESTICULAR SEMEN OF THE AFRICAN CATFISH CLARIAS GARIEPINUS (BURCHELL, 1822) AND ITS RELATIONSHIP WITH FERTILIZATION AND HATCHING SUCCESS
4. CARBOHYDRATE METABOLISM OF EGGS OF THE WHITEFISH, COREGONUS SPP. DURING EMBRYOGENESIS AND ITS RELATIONSHIP WITH EGG QUALITY

From: jxaguirre58@yahoo.com
To: shrimp@yahoogroups.com
Date: 6 October 2005
QUESTION:
Is anybody still using uncoated concrete (cement) tanks for larviculture? How about coating the tanks with beeswax, is anybody doing that? I am trying to find an altenative to refinishing tanks with epoxy paint.

J.X. Aguirre jxaguirre58@yahoo.com

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COMMENTS 1:

I don’t recommend the usage of uncoated concrete tanks for larval rearing. Beewax is a cheap option to cover concrete but life is short , the other 2 options I see is epoxy paint and liners, both work good for larviculture. There is a type of covering not as expensive as epoxy but very effective; it is covering concrete with a thin layer of fiberglass and finishing this with gel coat (boat finishing) is very good, lasts longer than epoxy. The only limitation should be the use of acid for cleaning, because this will shorten fiberglass life by half.

Jaime Baquerizo

COMMENTS 2:

I would say that most of the thousands of vannamei and monodon hatcheries in China, Indonesia and Taiwan are still using uncoated concrete larval tanks. During my time out there, I visited many hatcheries and most were that way. Having said that, the performance from these hatcheries was way below par, with most of these hatcheries in the 20-40% survival range. However, the lower than average results may not have been from the lack of tank surface coating, but from other less than optimal conditions and / or technique.

Todd Blacher

COMMENTS 3:

It is my experience that concrete tanks yield better survival and continuity than epoxy coated tanks. Concrete tanks need to be polished for (we use a kind of stone to rub off the surface) extra smooth surface without any cracks or minute holes.

M.Chandrasekar

COMMENTS 4:

Concrete tanks which are generally rectangular can be expensive to construct and maintenance can be costly if not properly constructed. From our experience we use circular fibre glass tanks in 8 and 12 tons capacity and maintenance and cleaning operation are easily done.

Jimmy Lim
aolim@venturefarm.net
www.venturefarm.net

COMMENTS 5:

I totally agree with Chandradekar, the concrete tank is ideal, the older the better, smooth surfaces, no holes or cracks AT ALL. Just cure the tanks (if new) for at least one month or more as new cement/concrete will play havoc with your PH. Smooth, shiny concrete walls, the best and the cheapest. In wide use all over Asia.

Alec Forbes

COMMENTS 6:

While I agree that looking only at the initial installation costs of concrete hatchery tanks - they are the less expensive than fiber glass tanks in many parts of the world. However, they are not the cheapest larval tank alternatives and you should also examine secondary cost factors when comparing concrete tanks to epoxy fiberglass tanks. Here are some things to consider when making your hatchery tank choice:

MAINTENANCE AND CLEANING - I have seen very few concrete tanks that ultimately did not crack and leak - at least some. Those concrete tanks that have some surface sealant - require periodic resurfacing. Concrete is also not nearly as "clean" as non molecularly water porous substances such as food grade epoxy fiber glass (note I said epoxy and not polyester type fiber glass - which is water porous). Even the smoothest concrete has surface irregularities, microscopic surface pores, and fine cracks that can harbor organic goop (don't mean to get to technical here), bacteria, fungal spores and viral particles. Depending on the
size and depth of these voids in the concrete surface it can make effective sterilization between production runs and disease outbreaks very problematic. When concrete tanks have deep cracks they can't even be sterilized with steam cleaning - because the concrete mass has such a large heat sink capacity - it makes the steam cleaning process ineffective except for direct exposed surfaces. You should also remember that concrete is highly reactive with acids - where as epoxy is not. If you use acids to clean you will erode your concrete surface even more. When you erode to the point that you expose the concrete aggregate the surface of the tank will take on a lunar surface texture - that can't be "rubbed out" and will have to be resurfaced... again and again. So, your choice of cleaning and sterilization agents is also
limited by tank material choice - especially if its concrete.

ADAPTABILITY - Finally, the "best" and generally the most valuable commercial aquaculture facilities are generally those that are most easily adaptable. Adaptable to expansion, new technology, scaling up or scaling down, remodeling, redecorating, etc... Its tough and next to impossible to effectively move a concrete tank. Another negative factor
with concrete is the difficulty in installing and sealing any through-the-wall fittings - say to install a heater or a pipe fitting. A concrete tank requires a hammer drill, and or a hammer and a chisel, gloves, safety goggles, and a couple of hours to a couple of days to
make the final product... which has a 95% probability of leaking if not when completed... soon. Epoxy fiber glass tanks only require a hole saw, a standard PVC bulk head fitting and about 15 minutes. If it leaks... tighten the bulk head fitting.

VALUE - At least with epoxy fiberglass tanks they can be moved around, taken in or out of a facility, exchanged for larger or smaller sizes, stacked in a corner while your facility is reorganized, replumbed, rebuilt, rewall papered or completely resterilized. This portability of
fiber glass tanks means that the value you have invested in your portable epoxy fiber glass tanks can be at least partially - if not totally (considering the recent doubling in oil prices) recovered if you want to sell them - one at a time or all of them. Concrete tanks on the
other hand have no second hand value - unless someone wants to buy and use your entire hatchery facility exactly as it is. (Epoxy tanks are bankable assets with bookable value - concrete tanks are not other than as part of a profitable facility).

CHEAPEST OF THE CHEAP - If you are on a "shoe string budget" trying to "boot strap" your operation (good luck in translating these colloquialisms) then hard epoxy fiber glass tanks may be too expensive. However, there are alternatives that are even cheaper than concrete tanks. There are quite a number of commercial hatcheries that use free
standing or framed plastic (HDPE) liner tanks (similar in design but much more durable than backyard above ground swimming pools) very cost effectively - cheaper than concrete - anywhere, and cheaper than epoxy fiberglass - everywhere. If you are using HDPE liner type tanks - just remember that they have to drain effectively so they have to be set on a
cone shaped sand bed (with concrete drain fitting collar base) or cone shaped concrete base. Then you can drain, harvest your pls and clean these tanks more effectively. HDPE does weather, scratch, and abrade more than epoxy, but less so than concrete, it is not affected by acids and therefore is much more cleanable than concrete.

From an economic value an adaptability standpoint, I don't think there is a question that portable epoxy fiber glass tanks are the best value in the long run because their value is recoverable and their ability to be re-used increases their initial and their long term inherent value. If you are comparing concrete and epoxy - remember to look at their
respective value in 5 years as part of the purchase comparison. If you are in a tight budget situation where you can't import HDPE for liner tanks and you have concrete and concrete artisans available - then you go with concrete because they definitely work - to some degree more or less depending on the builders and the users. Based on my experience - concrete would be my last and absolutely forced choice for any hatchery tanks - for all the above reasons.

Durwood M. Dugger, Pres.BCI, Inc.
duggerdm@bellsouth.net

COMMENTS 7:

I don’t totally agree with Mr. Chandrasekar’s assumption. Through my few year experiences working with concrete tanks, wood/liner tanks, fiberglass and also plastic tanks in larviculture I got fine result from each one of them. I agree that concrete tanks, in some cases, are cheaper than others, but concrete requires more maintainance, if you want to keep good result along the years.
If you have concrete tanks, a key to avoid problems later is to maintain an appropriate procedure to disinfect them. As an example, the epoxy coated will be affected if you brush walls with chlorine or acid.

Robinson Bazurto

COMMENTS 8

Robinson,
That is not my assumption but my experience with epoxy coated and uncoated concrete tanks. Apart from better survival, I get darker PLs (monodon) and quick start between runs. I would say I am more comfortable with uncoated concrete tanks than epoxy or other tanks. This is particularly practical for large larval rearing tanks seen in Asian countries.

M.Chandrasekar
Aquaculture Manager
Oman Fisheries Co SAOG
PO Box 2900
PC 112, Ruwi
Sultanate of Oman
Phone: +968 24509544
Fax: 24597804
Mobile: 99523620
Email: aqua@omanfisheries.com
Web: www.omanfisheries.com

AQUALAB TRAINING COURSE “QUALITY OF FISH PRODUCTS"
This is the fourth in the AquaTT-led, Marie Curie funded series known as AQUALABS. The course will take place between 12 - 17th December 2005 inclusive at University College Cork, Cork, Ireland.

Targeted at PhD level students and early-stage researchers, 25 funded places are available on the course. Funded places cover the €700 course participation fee as well as the majority of travel and subsistence costs. Five un-funded places are also available for the private sector or students able to avail of external grants. Please contact AquaTT if you would like to apply for one of these places.

The application deadline is 28th October and complete applications (CV, application form, motivation letter, recommendation letter and Proof of Identity) must be sent via e-mail to lorraine@aquatt.ie

If you require any further information please visit the AquaTT website, www.aquatt.ie

Ms. Lorraine Rafferty
Project Officer, AquaTT
PO Box 8989, Dublin 2, Ireland
T +353 1 644 9008, F +353 1 644 9009
lorraine@aquatt.ie

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