Zebra Danio With A Crooked Back

Hello,
I just got home from work and went to admire my 6 gallon tank (Eclipse system 6) and one of my danios is lingering in the back of the tank just above the heater, with a severely crooked back. They all seemed fine last night. I've had the tank for about 5 and a half weeks, and just finished with the nitrogen cycle, so I don't think it is a water quality problem. I did notice one of the fish looking rather plump last night, but none look pregnant today...is it possible that this is the fish that was pregnant, and it is just recovering? It looks rather sickly...see the picture.

The tank readings as of yesterday are:

Ammonia 0
Nitrite 0
Nitrate 10
Ph 7.6
tank temp: fluctuates between 75-78
I Don't have test kits for kH or gH.

Volume and Frequency of water changes: 20% every 4-7 days

Chemical Additives or Media in your tank: Stress Coat with each water change.

Tank inhabitants:

5 zebra's, 2 gold honey dwarf gouramis, 2 otocinclus catfish
Java Fern & Anubius

Does anyone have any idea what could be causing this, and why it happened so suddenly (literally overnight)? Thanks for any help!

Tanks overstocked, danio need larger tanks as they are very active fish.
The tanks to small for the cat fish.
Bent spine, injury, internal parasites to fish tb.
Check the amus of the fish to see if its enlarged or red and inflamed.
What does it look liike when the fish goes to the toilet.

Wilder said:

Tanks overstocked, danio need larger tanks as they are very active fish.
The tanks to small for the cat fish.

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So the "overstocked" tank caused the fish to get a deformity overnight? I do plan on up-sizing the tank, but I will be moving at the end of June, and I don't want to move 2 tanks. By using the 1 inch of fish for each 10 inches of surface area, I think I'm stocked at about 75-80%. I'm not planning on adding anymore, but I don't want to get into an argument about the number of fish in the tank either...I want to determine if there is any way to help this fish, or if I should put him out of his misery.

Wilder said:

Bent spine, injury, internal parasites to fish tb.

Click to expand...

I'm not sure I understand this statement...Is this your diagnosis?

Wilder said:

What does it look liike when the fish goes to the toilet.

Click to expand...

The fish bottom isn't enlarged, red, or inflamed. I haven't seen it poop since the crooked back appeared.

No the overstocked tank dosn't cause bent spines.
If the fish looks distressed and in pain yes I would end its misery.
Here are some reasons a fish may develop a bent spine.


If born that way, the fish may have a genetic abnormality.

If born that way, the fish may have incurred a developmental problem while growing inside the egg. This could be related to diseases, temperature, injury, etc.

If the fish was shocked via a faulty heater, pump, etc. or via lighting (striking a pond or surging through a house), this can result in a bent spine.

A severe injury can bend the spine. Normally though if broken, the fish would die right away.

Fish tuberculosis sometimes results in a gradual development of the curvature of the spine. I have seen this often in zebra danios but also in a golden orfe and a few other species. A fish with this condition (fish tuberculosis with a bent spine) is often also anorexic. See this section for more on fish tuberculosis.

Certain vitamin deficiences can result in spine curvature.

It seems that many fish nearing the ends of their lives get bent spines which usually match one of the above problems but sometimes do not.

Just in case for symtoms to look out for.
http/www.4qd.org/Aqua/disease/tb.html

Hi Lenny. Sorry to hear about the danio. Wilder's right though; you're massively overstocked, I'm afraid. I'm not sure where you got the inch of fish to surface area thing... the only rule of thumb like that I've ever heard is one inch of fish (fully grown fish) per gallon. At that rate, I'm not sure even the 5 danios on their own can be kept in there. The danger of being overstocked is two-fold. First, you've got a lot of fish in a tight space, and that's likely to cause some stress. Stress lowers a fish's immune system and makes it more susceptible to disease or illness. Secondly, over time, your tank just won't be able to handle the bioload and in such a small tank when things go bad they go bad quickly with tragic results for the fish. I'm sorry; I know that's not what you were hoping to hear, but I wish you luck!

As the 2 other posters have already told you. That tank is severely overstocked. The general rule is 1 inch per GALLON. And even then, you have to take into account the fish's full grown size, how active the fish is and how much waste the fish produces.
Although danios stay fairly small, they're very active fish and should be kept in a larger tank.
I'm not familiar with the other 2 types you have but I'm sure someone else will be able to inform you if they're ok in the 6gal.

As for the poor lil danio with the bent spine... I have no idea. What Wilder says though is good info and good advice.