How many inches long is the eel?
What is the usual water temperature of the tank?
What kind of substrate is in the tank?
Are there any kind of "hiding places", i.e. large rocks, tubes, etc., etc., in the tank?
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The eel is about 4 inches. Water temperature is about 75 F. The water tank doesn't have any "hiding places". It only has one big artificial algae (plant) in the center and a couple of small artificial plants on the sides. In the past it used to hide underneath the the gravel on the bottom of the tank, usually showing only its head. What do you mean by substrate?
Thank you for the information.
Substrate is the material on the bottom of the tank, i.e. gravel, sand, etc.,etc.
You mentioned that there is gravel at the bottom of the tank so basically you've supplied with the information needed concerning substrate. Note: Smaller sized gravel or sand is better suited for peacock eels as they are burrowing fish as you have seen.
Your eel is suffering from an ailment called Swim Bladder Disorder (sbd) which is a disorder that affects a fish's swim bladder. The swim bladder is responsible for a fish being able to swim correctly and maintain its buoyancy. When it becomes blocked, infected or too full of air it ceases to function properly as you are witnessing with your fish.
Many types of fish are highly susceptible to this disorder mainly because of the odd shapes of some species, genetics, poor breeding practices and sometimes diet.
There really does not exist a fool-proof way to prevent sbd but by maintaining excellent water conditions and soaking flake food prior to feeding can lower the prevalence of the disorder. The reason for soaking flake food, prior to feeding, in tank water set aside, is that the flakes will absorb water thus lessening the amount of air the fish intakes while eating.
The traditional way to treat this is by isolating the affected fish in a quarantine tank using water from the main tank so as to not change the fish's environment too much.
If the fish is the only fish in the tank then there's no need to seperate it. If you can't seperate the fish then the only alternative is to treat the whole tank. The recommendations below should not harm the other fish is you decide to treat the whole tank.
Once seperated begin to feed the fish canned peas without the husk/shell. Feed 1-2 peas twice a day making sure to clean out any uneaten portions. Peas are well known to clear out a fish's swim bladder. It's best to feed the pea diet exclusively. If the pea diet does not work then try the pea diet with intermitent days of fasting.
In addition to the pea diet you can try treating the fish with a medicine called Maracyn-Two (USA)) which could prove helpful in curing sbd as some cases are caused by bacteria although I tend to believe this problem is related to the fish's diet. Listed below is a link which will show you Maracyn-Two.
It would also be helpful to not fill the fish's quarantine tank up to the top with water leaving about 2-3 inches from the top free as this will lessen the amount of water pressure on the fish.
Please keep in mind that sbd can sometimes be very difficult to cure and is one of the
most common problems fishkeepers face.
Listed below are 2 links which will further elaborate on sbd.
Best wishes and please let me know if you have any questions.
http://www.drsfostersmith.com/product/prod_display.cfm?c=3578+4615+4842&pcatid=4842
http://badmanstropicalfish.com/forum/index.php?topic=1026.0
http://www.fishdeals.com/fish_diseases/swim_bladder_disease/
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