Build a test tank for your streamers and wet flies for 20$!

Every fly fisherman likes to watch the action of the flies in water before using them in fishing. Especially if you tie your flies by yourself you must be really interested to see how they are swimming and acting in the river. You may also try to ask the fishes about the action of your flies, but sometimes it is quite difficult to understand the result..

You may try to test your flies at home in the bath but the easiest way is to use a test tank with running water. In the transparent tank you can watch the fly from the side and even from below. You may buy a test tank but it is easy to build it also by yourself.
To test the action of the wet fly in a right way the flow of the water in the tank has to be laminar (steady) with no major turbulence (whirls). It would be also practical to adjust the flow speed of the water. In the present test tank model the steady flow is achieved by pumping water to flow around in a narrow space (2") between two circular round vessels.

What do you need?

1. pump, eg a bilge (boat-bottom) -pump with output of 1200-3000 liters/hour. It works with a 12 V battery or a small AC-DC adapter. You may even use a "garden-pump" connected to an electric drill with same output power. The aquarium -pumps are not strong enough.
2. a transparent round container /vessel, e.g. a plastic cake -cover with a diameter of 12" and height of 6".
3. a smaller white plastic container with a diameter of 8" and height of 6". White is a good background color for the flies.
4. a piece of plastic tube for the output flow (5") of the pump and a piece of wooden lath (20") to fix containers.

Construction (see the figure)

Put the vessels inside each others. Make some (4-5) small holes (1/2") to the walls of the smaller vessel. The pump (or the input flow of the external pump) is located inside the smaller vessel and the output tube of the pump is put through the wall of the smaller vessel to make the water run circularly between the vessels.

Fix the vessels and the pump using the lath, glue, some wire etc and pour the water in.

The pump takes the water from inside of the inner smaller vessel and keeps the water running between the vessels to make a circulating steady flow. You may also try bigger vessels and a more efficient pump.

WARNING: Please be very careful when using electric equipments in wet surroundings and near the water tank. There is a hazard of an electric shock!

How to test the fly?

Adjust the speed of the circulating flow with the output of the pump. Use a short rod (10" of wire or stick) and line (5") to sink the fly. Between the vessels you may find different speeds of flow. You are now able to watch the action of your fly from the side or even from below.

What have I learned?

The thickness of the tippet and the type of knot are very important to the action of the fly in the water. A loop knot seems to affect less.
Some of my streamers were swimming on one side or were not otherwise what I wished.
The shape and profile of wet flies (especially streamers) are totally different when looking from the side than from above. In some streamers the hook was too low compared to the body, wing and tail. I think that the shape and the movements of a streamer have to be lively like a small fish. Some streamers were, however, changing their shape too much if I changed the speed with jerks.
I have also observed the stiffness of hairs and the action of salmon flies in the tank.
Weight of the fly: the lead weight has its effects on the posture of the fly in the water.

Picture of the test tank?