Larvae Light Trap - Collecting Larvae from a Display Tank

[onsan]

Larvae Light Trap - Collecting Larvae from a Display Tank
The following is the method I use to collect Clownfish Larvae automatically overnight, the method is reliably effective and gentle on the fry and eliminates the need to keep watch for spawning and capturing by hand. This method should work for most free swimming night spawning fish and crustaceans that are attracted to light.

In principle, the trap is nothing more than a airlift and collection cup, much like that employed by a protein skimmer. Due to the larvae being attracted by light a simple glowstick is placed at the base of the riser to bring them within the intake current of the riser. The airlift in the riser draws the larvae up into the collection cup where they are held indefinitely. This allows the trap to be set in the evening and left to run overnight for removal in the morning.

The are 6 components in the trap;

Collection Cup
Riser
Airstone (and airline and air pump)
Mesh Screen
Glowstick
Magnets

I used a common tuperware container, 5L, approximately 200mmx100mmx250mm as the Collection Cup
The Riser is a 25mm clear plastic tubing, approximately 200mm long.
The Airstone a small diameter (~10mm) fine bubble airstone fed via airline from a diaphragm pump
Mesh Screen used came from some nylon material. needs to be fine enough to withhold the larvae.
Glowstick, green so far seems most effective.
Magnets used to hold the collection cup in position.

Cut a hole in the base to fit the riser, cut a hole in the side to fit the mesh screen, ensure the screen is in the top half of the collection cup to keep a well in place in order to conveniently relocate the fry from the display tank.
Fit the trap near the eggs, as close to the surface as possible using the magnets. the base of the riser is more effective the closer it is to the surface.
ensure that the top of the riser is below the surface so that the larvae are handled gently.

Please see the diagram and photos for construction and application.

http://onsan.gallery.netspace.net.au/Larvae-Collector

In the pictures you will see the glowstick is positioned immediately below the riser, as luck would have it the airstone i used fitted perfectly in an indentation in the base of the glowstick, this made it easy to position both the airstone and glowsitck in the riser.

At this point i would like to make a couple of recommendations. Fry immediatly swim to the surface upon hatching, for this reason it is favourable to have the intake of the riser as close to the surface as possible, to make this easier a wider rather than higher collection cup would have been better (hindsight). Cups less than 250mm high will be more effective in achieving this. Also, turn off all but the smallest pump to allow the larvae a chance to swim before getting pumped.
Fine bubbles and ensuring the riser finishes at least 20mm below the surface will prevent the larvae from being damaged during capture.
Ensure that the ends of the riser are smooth with no sharp edges.
Dose the cup with Rotifers, it will help survivals if they have a readily available feed source whilst being held in the cup overnight.
Be careful when removing the cup from the DT not to allow the larvae to drain back out of the riser, tip it over and drain some water using the mesh screen.

Well I hope you find this helpful. Now with a good nights sleep and a trap full of larvae you only have to raise them! only! Good luck.

[Octoshark]

Thanks for sharing

[ezhoops]

nice find, thanx

[Allmost]

nice !

would these work for bangaii cardinals ? I cant remove the male from the reef tank and he is about to trow the babies up :P