"Günther De Vogelaere" wrote
in message ...
When biologists try to chart the fishpopulation in open water, they
often
use electricity to stun the fish.
Maybe this is a silly question, did anyone ever use/try electricity to
catch
their (sick) fish out of a fully decorated tank?
Would this be a good idea? What current/voltage should be used?

The probability of finding the correct voltage/current ratio is very low,
while the probability of electrocuting yourself is quite high.

Lateral thinking. Do not chase the fish into a trap. Lure it. Select
an appropriately sized container (a pail standing in the water), and
always feed such that the fish need to go into the pail to eat. Do this
for a few days and then drop some bottom feeder pellets in so they have
to go to the bottom and lift the pail. Then scoop or net out the ones
you don't want.

Catching a fish in it's element is very difficult, and with enough
shelters, futile. Besides traps, accustom the fish to 2 large nets which
you leave in the water. After a few days (or perhaps hours), they are
swimming in & out of them. While pre-occupied with feeding, gently move
one net towards the other. Fish will always move away from the moving
object, backing into the stationary net. The trick is moving v e r y v
e r y slowly, and sometimes a small burst of speed (depending on how
suspicious they are).

Another technique is to place a large stone in the front corner of the
tank (with enough space for fish to swim around it). Then park a
stationary net on the side of the rock opposite the corner. Using a
chaser net, herd all the fish into a pack and push them along the back
and around the corner into the waiting net. In a crowd, the back fish
don't see the net and they push the front fish forwards, who are unable
to effectively turn around when they see the net. This works in heavily
planted tanks, but not in heavily rocked tanks.

Another technique (good for rocky tanks and aggressive eaters) is to hold
the net tight (no slack in the material) and when the fish come up to
feed, you do a quick dip into the water. It's all in the wrist action.
You really need to have the cover off and the fish need to be accustomed
to being fed with no cover, or they will be too suspicious.

Using these techniques, and other variations, I catch about 70 fish per
day out of heavily decorated tanks. The worst fish to catch....
Leporanus, with Pacus a close 2nd place. With both of these fish, I use
2 nets and basically manoeuvre them so the fish will stumble into the
large stationary net, while evading the smaller chase net. Leporanus
take 1st place because they achieve the longest airborne distances ;~)
The Pacus take 2nd place as they tend to keep going, even after being
netted! Both usually give me a shower unless I quickly grab them.

NetMax