3d Printed Pelagic Larva and Egg Collector

[DaJMasta]

The design has matured to a point where I think it works pretty well, and I find myself using this collector over the Vossen trap - it doesn't look as nice, but it's more configurable and much easier to transfer collected eggs and larvae out of.

 

That's the complete collection setup in action

 

This is the complete set of models available for download here: https://www.thingiverse.com/thing:6168731

You need to print several parts to get it going, and as a baseline you need:

One collector mount (thumbscrews as needed)
One surface skimmer (tall version is recommended)
One airlift pump (tall version is recommended)
One splash guard (superglue to the top of the airlift pump)
One holding basket with its mesh retainer

In addition, you'll need an air pump, tubing, and valve to run the airlift pump, and some aquarium safe mesh - I like 200-250 micron to catch most things and still have reasonable flow through.  This kind of fine mesh is usually nylon or polyester and can be cut out of a filter sock with the appropriate holes size - you don't need a big piece.

 

In the download I include the regular sized airlift pump and surface skimmer, but I don't recommend using them unless height is constrained, they just don't get as much throughput.

In addition to printing the parts, you'll need to glue on the splash guard to the top of the airlift pump (otherwise spatter will happen for sure) and you'll need to put the mesh over the window in the holding basket and then glue the mesh retainer to it.  I've used small drops of superglue around the perimeter and then just sandwich the mesh in there, works just fine.


To actually use the collector, attach the mount to your tank (using the regular model, use at least two algae magnets to secure the tabs to the side, using the rimless model, slip over and use the thumbscrews to adjust height/angle).  Then you drop in the surface skimmer (align the tabs on the outside of it, push it in, and twist to hold in place), and the holding basket (you can aim the mesh outflow wherever and can aim the surface skimmer input).  Then you put in the airlift pump and dial the airflow and holder height to get good flow into the holding basket and a water level slightly lower than the tank in the skimmer cup.  It collects best with the main pumps in the tank off (you also don't lose larvae to the overflow or pump blades), and the water flow through it helps oxygenate the tank somewhat - my tank can only go 1:15 or so with no flow until fish start panting, but with this going I've had them looking fine for hours.

When you've collected what you need, the holding basket is removable and will strain excess water to drop into a rearing vessel or transfer to a temporary holding point, like using the holding mount.  This other mount is sized for a 10 gallon rimmed tank (or any rimless, really) and the holding basket includes a spot for an airline to keep circulation in the basket.  I wouldn't leave swimming larvae in there too long, but it's big enough to hatch eggs in and is pretty safe (low suction when draining to transfer) when transferring very fragile larvae.

 

For phototactic larvae, make sure the room is otherwise blacked out and then put a dim to moderate light over the circular holder on the skimmer cup.  The light diffuser model included can be printed in transparent filament to dim a bright light and is sized to hold a Lumintop Tool AA flashlight.

 

A moderately powerful air pump should get you reasonable flow through the thing, maybe into the couple dozen GPH ballpark, but thanks to the air and the mesh output, should be gentle enough not to injure most larvae.  To speed collection and ensure you collect as many as possible, I usually hunt around at the surface with a cup to scoop up some extras and pour them into the basket with the others once I see the spawn has happened.

Print the unit in PETG - ideally food safe varieties, but that's not what I've done - in something opaque.  Black helps minimize confusion of larvae with stray light involved and generally looks good/doesn't grow too much.


Hopefully this design simplifies collecting somewhat while minimizing damage to the larvae when transferring and maximizing the circulation in the tank to allow for long collection periods without the pumps on.  It has certainly helped for me!

[DaJMasta]

Because there are a bunch of parts and it's hard to see everything all together, I made a little video running through the parts and its usage:

 

[therootcause]

Wow - outstanding job.   The insert and twist design for the skimmer cup was excellent forethought.   This is a much better design than the HOB refugium air lifter that I've been thinking of setting up as a larval trap.  I run the vossen trap overnight, but have been thinking of adding an air solenoid and an LED powered by one of the EB832's 24V DC accessory ports.  Have you thought about adding timers to the air lifter and light? 

 

 Reading the title I was hoping you actually printed a "Pelagic Larva".  If you do decide to print a larva please send via local post to A. Haynos, Lebanon, PA.  

[DaJMasta]

I haven't been using timers, and for the light you'd either have to modify the existing one or use something else, but I'm a bit of a night owl, so usually staying up to complete a  midnight or 1am collection isn't a big deal.  The timer could be useful, I suppose, but I also thing collecting larvae in the morning may just be too late in some cases - I've also seen that when you've got the Vossen trap going with larvae already in it, there is some tendency that they start piling up in the middle of the mesh portal - I think a combination of the output pressure and the swirling motion.  I expect that amount of clumping up would start to be harmful at less than an hour, and while not every larva will do it (and probably no eggs), I avoid running these things for longer than I have too once I actually collect something.

With the more chaotic flow from this pump and the slightly larger mesh area (maybe coarser mesh), maybe it would fare better - I at least haven't observed larva getting stuck to the output, but even then, there are larvae that if they're in this confined a space or they don't eat in the first night, they're not likely to make it.

The twist lock on the skimmer was an early change to the design - if your skimmer level is a little high, the pump pulls all the air out of it and it gets very buoyant - I ran into those trying to pop out very early haha.

[Kathryn Lawson]

This is brilliant! I tried to make a larval trap the other day based on a funnel design I found in an old Coral magazine with a 2L soda bottle - cut the bottom off, cut the top off and inverted it to make a funnel up into the main body of the bottle, and attempted to attach the top and middle with hot glue (and learned in the process that hot glue is hot enough to melt soda bottle plastic...), then glued on foam at the rim (originally the cut where I took off the bottom of the bottle) to keep it floating but it took some wrangling and doesn't pull from the very surface, nor does it have any air/water flow to help the larvae in or keep them moving/aerated once inside. I didn't have a light over it either, and it didn't seem to work - my sexy shrimp must have spawned overnight after I went to bed (female carrying eggs the night before, and not carrying them in the morning), but I didn't find any larvae anywhere (including in the trap) in the morning.

A USB-powered air pump would be really easy to put on a standard outlet timer, as would a small corded/USB-powered lamp! Combined with another air line to the bottom of the collection container to keep the larvae moving around, maybe it could work for overnight collection of less sensitive larvae?

[DaJMasta]

That's an idea, the main pump on a timer and then just a bubble or two a second in the holding chamber.  If your mesh size wasn't too big, you could even load it with food before you go to sleep to try and feed what you catch.  In the small space you'll still run into issues - collisions between larvae usually trigger a jump back, which uses a lot of energy, so the tight space is probably still working against you.

[therootcause]

2 hours ago, DaJMasta said:

I've also seen that when you've got the Vossen trap going with larvae already in it, there is some tendency that they start piling up in the middle of the mesh portal

 

I have seen the same thing with my (presumably mysid) larvae.   By morning they are swirling around the center of the Vossen and bouncing off of the mesh.  This can last for several days as they stay suspended and seem to be unharmed.  Not that I recommend leaving them in the trap.  Like @Kathryn Lawson, my shrimp have carried eggs yet I struggle to get them into the trap.  My return pump ramps down at night and two of my three powerheads turn off.  I may shift the light schedule forward two hours so that I have more time to stay up and collect and relocate. 

 

Have you seen this breeding site?  http://www.mbisite.org/Species.aspx  

 

@Kathryn Lawson you may find this link specific to Sexy Shrimp breeding journals helpful.  http://www.mbisite.org/Search.aspx?Species=181

[DaJMasta]

A little update, there's a new model uploaded for the mount for the collector that fits a standard rimmed 10 gallon tank as well, now, whereas before it would have held the equipment at an angle if tightened down.  Should probably fit some other (at least smaller) rimmed tank sizes, and basically just replaces the "rimless" version originally uploaded.