Printer-friendly versionPDF version

 

Building a Budget Larval Snagger

 

Caveat -- this is a DIY in progress should be completed within the next few days!

Here is a design for a well working larval snagger (and a few variations) I built after realizing I needed one.  The design is quite simple and can be made rather cheaply using easily obtained items.  Best of all it works very well.  While emptying / collecting the larvae from the snagger is still a problem I'm working on (see revision C:) I've had excellent luck with this.

 

It must be stated that I built this based on a design found at the MOFIB forums posted by Amie, there have been many other contributing threads with many authors giving me ideas such as KathyL and Armagedon48, they're a good group.  Find the threads here:

http://www.marinebreeder.org/phpbb/viewtopic.php?t=499&highlight=

 

and here:

http://www.marinebreeder.org/phpbb/viewtopic.php?f=141&t=499&start=0&hilit=larval+snagger

And off to the races we go!!

 

Materials Needed:

• Empty bottle of preferred size (I like the 16 ounce tea bottles)
• Sheet of fine mesh, bridal veil, filter mesh, screening all will work
• Two (2) 1/2 inch PVC TEE's
• Two (2) 1/2 inch PVC Elbow's
• approximately One (1) foot 1/2 inch PVC pipe (mistakes happen)
• A file or a strip of sandpaper
• Knife or razor blade
• Some 100% Silicone caulk (I use the Silicone I)
• Adequate lenght of rigid or "Thinwall" airline (I use 3/16" thinwall, around 8 inches should be enough)
• Airline tubing
• Air pump
• Air valve and Tee (to set flow and bleed off extra pressure)
• Light source (led, flashlight, etc.)  This will change with each revision (as Revision C utilizes a built in LED).
• Clamp to hold snagger in place in the tank (find out what suits your environment).
• Pipe cutter or hacksaw
• 3/8 inch drill bit (and naturally a drill or drill press).
• Measuring Tape
• Marker (sharpie)

 

 

Lets Get Started!!

 

First, you will want to cut three (3) 1 1/2 inch peices of the 1/2 inch PVC pipe, these will be used for the upper cross pipe, lower cross pipe, and the bottle attachment.  I chose 1 1/2 inches as each Tee and Elbo has a 3/4 inch deep stop for setting the pipe, this makes the cross pipes compact and saves on space as well as reduces the amount of travel the larvae have before reaching the collection bottle.  Less travel = less possibility for damage and loss.

 

`

 

 

We will then measure our bottle for height so that we can cut our vertical pipes.  I prefer to keep most of the bottle submerged as this allows me to increase surface area of my screen reducing harsh flow within the bottle (keep from pushing the larvae up against a small peice of screen) as well helps to avoid clogging.  My bottle is about 8 inches tall and I am not concerned with the depth of my tank so I will make my vertical pipes about 7 inches long.  Considering the Tees and Elbows will add around 1/2 inch each to the height of the below surface part of the device I am about 8 1/2 inches below my water surface.  The water line will be just above the center of the Tees on top so I will have around 1 inch of bottle and Tee out of the water.  Because I prefer my inlet pipe to sit just a bit lower than the apparatus (preference really, I havent found any major benefit) I will cut the first vertical 7 inches and the second at 8.

 

 

 

It's a good idea to file the ends of each pipe so that you can easily take the apparatus apart for cleaning, storage, and of course larval removal.  I file the third 1 1/2" inch peice (the one that will hold the collection bottle) down enough that I can slip it in and out of the bottle with ease.  I also have a tendancy to file one end of my top cross pipe a little further so that I can separate the sides without having to twist.  Both of these are to allow me two different and easy ways to remove the collection bottle without shaking up or losing larvae.

 

For your collection bottle you will want to cut an opening in the side of the bottle and silicone your mesh against it.  I typically cut this about 1/4 inch above the waterline and extend it down to just above the center of the bottle.  I will cut it nice and wide spanning around almost half the bottle.  This gives me a good sized outlet to reduce forcing the larvae against the mesh.  Silicone the mesh over the opening and then let it cure for about 24 hours.  It's a good idea to run a second bead of silicone after the first one cures.  This keeps a good tight seal.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Lay out and assemble the collector as shown.  The theory here is that an airline will connect to a peice of rigid placed within the uplift pipe.  The rigid will extend almost to the bottom of the pipe but be set up about 1/8-1/4 of an inch, a light can be placed at the bottom of the pipe (as in revision C) or at the top placed within the Tee to attract larvae to the bottom of the pipe.  The suction created by the air bubbles (ala airlift) will pull the larvae up and across the top crosspipe, down and through the bottom crosspipe and then up again into the capture bottle.

 

 

In revision B I drilled a hole in the side of the first Tee above the cross pipe, this allows me to take a peice of rigid, heat and bend a 90 degree angle and actually place the rigid in the pipe with it's inlet coming out the side, this makes for less problems with clamping and holding the rigid, as well as keeps the top of the Tee open for a flashlight to fit in better.

 

 

 

 

 

 

 

 

 

 

 

In revision C I drilled a hole in the side of the inlet pipe at the bottom so that I could place an LED directly there, I noticed the flashlight up top illuminated the PVC pipe at the top and larvae were attracted there as well.  This was not desireable as I wanted as much captured as possible.  I connected the LED to a pair of wires and covered with several peices of heat shrink tubing to keep it waterproof.  The LED was then connected to a resistor and powersource.  For those of you who arent electronics geeks I'll do a quick LED primer...

LED Primer

To wire your LED to a power source you will most likely need to drop the voltage of the power source itself to avoid damage to the LED.  We do this with use of a resistor.  First your going to need to find your power source!!!  You can get a wide variety of battery holders and ac adapters from radio shack or other supply stores but chances are you have an adapter laying around from that dead cordless phone or cellphone charger that you no longer have the phone for.  In any case you will need to know two things about your power source!  Voltage, and of course polarity (which wire is positive and which is neutral).

Now, once you know those you will need to know about your LED.  The LED has two leads coming down from it, the long and the short if you will.  Current (electricity) travels from positive to negative, the way the LED works is that there is an Anode and a Cathode.  The Anode is the long lead and this will hook up to the positive side of your circuit, the cathode is the short side which will connect to negative.  All LED's have a particular operating voltage and if we go too high we will damage the LED so we will have to know the voltage of the LED itself.  This may be on the packaging if you purchase the LED separate but if you salvaged it from a flashlight or some other device you may have to guess.  A good general rule of thumb is that most red and green LED's will operate around 2.2 volts and most blue and whites operate around 3.5 volts.  This is very important as you will need to calculate the size of your resistor to drop voltage properly.

Based on your supply voltage, and LED voltage you will size your resistor to drop the current just right.  Since I'm really not up to giving a primer on electrical design I will point everybody to a very useful site.  http://metku.net/index.htmlsect=view&n=1&path=mods/ledcalc/index_eng

 

Use of the Collector

Since my tank has a lip I use a spacer to clamp the collector into place.  I use simple woodworking clamps that can be purchased at home depot or most any hardware store fairly cheaply.  For a spacer I found that a plastic tray that .45 Caliber ammunition is packed in works perfectly.  Since I remove one entire side of the collector for larval transfer I clamp only the inlet tube side's Tee, this way when I need to empty the collection bottle I can pull the downdraft tube, Tee, and bottle away and lift the whole side out of the tank.  I used to pull the bottle up (placing thumb over opening to avoid spillage) but found this to be a little too difficult.  In the original threads that prompted this device most people cut the bottom of the bottle off and siphoned the larvae out.

(need to add pics of use and operation)