Date: 18 January 1999
From: yoram hoffman <yorhof@hotmail.com>
To: BRINE-L@UGA.CC.UGA.EDU
QUESTION:
We have been using A1 Selco for Artemia enrichment. It usually works well for us, but with some batches of cysts, it kills off the nauplii.
Has anyone encountered a similar problem?
Yoram Hoffman
Ardag
Israel
***************
COMMENTS 1:
Whenever I had problems with a Selco it was most of the time due to too low an oxygen level in the tank or too much Selco being administered.
Steve Geerts
e-mail: stevege@hotmail.com
***************
COMMENTS 2:
We've found that an overdose of the Selco relative to the number of nauplii has killed off the animals, probably because it fouls the water.
Nancy Lightowler
e-mail: nlightowler@lbaop.org
***************
COMMENTS 3:
The A-1 SELCO that was discussed is formulated to inhibit bacterial blooms during incubation of Artemia cysts. I have contacted our INVE Technologies to respond to the inquiry as this is the first I have heard of nauplii dying because of A-1. It was mentioned by Steve Geerts that sometimes a problem can occur with the emulsified SELCO's if close attention is not paid to DO. However, associated bacterial blooms (which cause oxygen depletion) are not known to occur with the A-1 SELCO. The A-1 line of products were developed to use during incubation of Artemia cysts in order to keep the hatching medium bacterial free as possible and to provide early enrichment.
Howard W. Newman
Inve Aquaculture, Inc.
e-mail: BShrimp@aol.com
***************
COMMENTS 4:
The A1 line stands for all in one: an enrichment at high density
combined with a continous disinfection during both hatching and
enrichment all in the same tank.
The A1Selco's can be used in three ways:
1. combined hatching and enrichment (in the same tank), using
decapsulated cysts.
2. short term hatching and enrichment procedure (in the same tank)
using decapsulated or non decapsulated Artemia cysts.
3. combined hatching and enrichment, followed by a subsequent
enrichment after separation, using non decapsulated Artemia cysts
In all cases it is very important to follow the right instructions for
use, extensively presented in the A1 technical card (Inve Aquaculture
NV, Belgium). Only when these are correctly applied the desired results can be obtained.
In short this means that one has to start with clean, disinfected,
neutralised tanks, equipment, water. The hatching and enrichment
conditions should be optimal; ie of the right salinity, at the optimal
temperature (28-30°C), enough light provided, strong aeration, minimum oxygen levels of 4ppm and pH controlled (pH should range between 7.5-8.5, by adding bicarbonate and/or NaOH).
The right preparation of the emulsion is also of primary importance:
mixing 50-100g product/liter water for 3 minutes with a kitchen blender and adding in several ratios the required concentration.
If all this is respected the advantages of the A1 Selco will be
clear:
- enriched Artemia of high nutritional value
- bacteriological control during the complete Artemia production
cycle
- increased enrichment densities
- increased Artemia production capacity
- reduced time and labor need
Marleen Dehasque
R&D coordinator Aqua Division
Inve Technologies NV
Oeverstraat 7, 9200 Baasrode
Belgium
Tel.: 32 52 331320
Fax: 32 52 334531
e-mail: m.dehasque@INVE.BE
***************
COMMENTS 5:
What, if any antimicrobial agent(s) are present in A1 Selco? Or does the baceriological control come solely from the hygenic procedures you mentioned in your original note on this subject?
Craig Bingman
e-mail: cbingman@netcom.com
***************
COMMENTS 6:
I doubt very much if Inve Technologies would go spread out the
composition of their Selco ranges ...
The bacteriological control does definitely not come solely from the hygenic procedures.
The use of disinfected tanks and equipment is mandatory, yet not paid enough attention to by most people. You will never ever get completely sterile or disinfected equipment but you should start with as low an initial bacterial load as possible. I take it that you know that glycerol is being released in the hatching medium upon hatching of the cysts. You will also have a leaching of nutrients from damaged cysts in the medium. All this forms a perfect feeding ground for bacteria to thrive on, so the development of a significant population of bacteria in the hatching cone/tank is inevitable during hatching. These bacteria will increase the BOD, produce unwanted metabolic wastes, and will be introduced to the media you keep the organisms to be fed in. Do also not forget that 6 to 8 hours after hatching, the nauplii start opening their mouth and anus, which will enable the bacteria to "invade" the nauplii gut "en masse". This is the reason why nauplii need to be harvested and rinsed before you (try to) keep on culturing and/or enriching them or transfer them into the tanks of the organisms you are trying to feed. This rinsing lowers the bacterial load on the nauplii again. You can also lower the bacterial load further by disinfecting the hatched nauplii by means of short time submerging in a disinfectant followed by direct neutralisation of the disinfectant. It speaks for itself that this procedure has the potential danger of killing your entire batch of nauplii if you make a mistake, e.g. wrong concentrations, wait too long, etc.
The use of an A1-Selco would simplify things; I do not know as I did not try this particular Selco yet.
Nevertheless, I am a little bit puzzled with point 2; what do you mean with "short term hatching"? In order to enrich nauplii one has to enrich at least for 10 hours after hatching of the cysts, right? So this means that one will have to leave the cones/tanks for at least 34 hours, preferably even a little bit longer. Do you call this short term hatching or do I misinterpret something?
Steve Geerts,
San Francisco Bay Brand
e-mail: stevege@hotmail.com
***************
COMMENTS 7:
I thank all who tried to help solve the mystery of Selco-A1 use. Having used it for some time now, I am still not sure it's worth the trouble and price (compared to ALGAMAC 2000, for example), and we have to make some more experiments. When that is done, the results will be published on the net.
Yoram Hoffman
Ardag ltd
Israel
e-mail: yorhof@hotmail.com