The bottle trap is ideal for well planted tanks where the size of the trap needs to be as small as is needed.
You make the trap using a plastic bottle. Usually, a soda bottle (or similar)- 1 or 2 quart size works. What you do is to watch the first 60 seconds of this vid and then close/stop it.
You can do this with an assortment of plastic bottles of different sizes. But, for them all, the opening is the same. There are plastic bottles with wider mouths you can find if needed. So what is next? This is how I do it.
I want to attach the inverted top to the bottle body. I do this by inserting the inverted end into into the bottle as in the vid and I align the edges together. Them I poke three holes around the perimeter which go through both pieces. When the bottle is finally ready to be submerged in the tank, I use three small nylon wire ties to attach the two pieces via the matching holes I punched. I trim the excess off of the tie after pulling it closed. But I leave a bit of slack so that when it is time to open the bottle, I can easily cut the wire ties off.
If you do not have small wire ties, anything similar you can tie would work or use anythin you can come up with as long as it will undo. Use your imagination, just be sure whatever you use is tank safe.
You need to put bait into the bottle to attract the fish. Make sure to use food that the target fish likes. You also need to weight the bottle so it sinks easily and stays in place. Large gravel or a few small rocks work just fine. Once the bottle is loaded, insert the lid and attach it via the holes. Submerge it just above the surface to fill it and then lower it to the bottom of the tank.
Important Considerations
1. Be sure that the bottle is well cleaned and that the label, and any glue involved to hold it in place, are be removed. Also, if there is a colored ring around the neck, remove it.
2. Make sure there is open space in the tank where the bottle can go when placed horizonatally.
3. Be sure the bottle size (after the top is cut off and inserted) can fit in the space you plant to put it.
4. Starve the tank for several days before you put in the trap. This helps to motivate the fish.
Why does this trap work?
It is easy for the torpedo shaped fish to fit in the opening. It just follows the "smell" in. A fish can clamp it's fins, so even a "fatter" fish can still enter (up to a point). But when it comes to getting out the problem is the bottle is clear, so for the fish finding the exit and getting properly aligned to execute an exit from the bottle is quite difficult. There is no scent trail to help.
However, every now an then a fish does get lucky and makes it out. So it helps to monitor the trap several times during the day to reduce the odds of this happening before you can pull the bottle with the fish inside.
