BY CHAZ STEVENS AND JENNY BRADLEY
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The following is a day by day account of the method currently used at Kingswinford Aquatics to raise common clowns and black and white clowns.
Hatch night
The larvae tank, 18�x 10� x 10� is part filled (5� deep) with either water from the parents tank, or newly made salt water, it does not seem to make any difference to the hatch rate.
To this another gallon of fresh water is added, this brings the s.g. down to around 1.018, this makes the eggs denser than the surrounding water, they then have a tendency to absorb the surrounding water and have a better hatch rate. the newly hatched larvae also exert less energy maintaining there osmotic pressure and so seem to survive better.
The pot with the eggs attached is placed in the larvae tank with an open air line placed by the egg mass producing a strong air flow passing over the eggs. the top of the larvae tank then has a piece of egg crate placed on it, and a piece of A4 paper placed on this. this is the light diffuser which will be kept in place for the next 10 days.
The whole of the tank is then covered with a bin liner to totally block out any light and the eggs are left too hopefully hatch.
Day 1
On the morning of day 1 the bin liner is removed and the air supply stopped. This allows you to see if the hatch took place.
Hopefully the larvae tank is full of hundreds of 3mm long larvae swimming aimlessly through the water. If this is the case the pot that had the eggs on it can be removed and the depth of water in the tank can be reduced to around 2� deep.
The air supply is turned back on, this obviously airates the water and also helps keep the rotifers and algae in suspension.
By reducing the amount of water in the larvae tank you greatly reduce the number of rotifers needed to feed the larvae. For the first 3 days you do not actually feed the fish as such, you feed the total volume of the tank. The larvae do not actively hunt for the first 3 days, they just drift around and bump into the food items, so enough food has to be in the tank at all times to ensure they do not starve to death.
At this time we also add live phyto plankton, the food item for the rotifers. This does 3 things, it keeps the rotifers well fed so that the larvae have an optimum diet, the algae burns up the ammonia and nitrites produced by the larvae and rotifers, and the larvae actually swim around in the water column better because side lighting is reduced, which means they do not �climb the walls�, swimming against the side of the tank, looking at their own reflections and not feeding.
Twice a day the rotifer density is checked by immersing a small glass into the larvae tank and simply looking how thick the rotifers are. If the rotifer concentration is too low the larvae will starve. Rotifers are added as required for the first 7 days. The live phyto algae density is also maintained on a twice daily basis.
Day 2
The first water change takes place today and this procedure is followed every day until the larvae tank goes onto the �mini system� usually around day 10.
Water is removed from the larvae tank by simply syphoning through a rotifer sieve that has been immersed in the tank. this leaves the larvae and rotifers in the larvae tank.
Freshly made salt water has a few drops of iodine added to it and is placed in a 5 litre ice-cream tub. the ice-cream tub is placed above the larvae tank and a syphon is made using air line, the new water is then allowed to top the larvae tank back up to its required level. Note, the water level of the larvae tank is increased as the larvae become more active and hunt more efficiently.
The water changes and use of iodine appears to improve the striping up of the larvae, we now get 95% of common clowns with perfect stripes, but still only get around 60% of black and whites with perfect stripes! We are at this moment experimenting, carrying out 2 water changes per day on the latest batch of black and whites to see if this improves the stripes. Jenny�s theory is that if the black and whites grow and stripe up quicker than normal clowns it may be that they absorb more of some unidentified substance out of the water, or that they simply produce more pollution that impairs the water quality, we shall see!
Day 3
Day 3 is basically a repeat of day 2, water change, add rotifers and algae.
Day 4
By day 4 the larvae have grown enough to be able to take freshly hatched brine shrimp, as well as rotifers.
At this time we also start introducing very fine powdered foods. dry foods are fed 3 times a day, always before the live foods, to encourage the larvae to take dry foods.
