Help - Threadfin Rainbows

[indigofuse]

Hi,

These are my first fish tanks.

I cycled my 20 gallon tank for 3 weeks.
Measurements taken yesterday are: pH = 7, temperature = 25, ammonia = 0, nitrite = 0.05, nitrate = 0

I purchased 5 Threadfin Rainbows 2 days ago as my starting fish. The pet store had only males and one potentially female so I puchased the 1 female and 4 males (websites recommend minimum 6 fish as they are schooling fish) They seemed healthy and active. Although the males are clearly aggressive - I imagine I started with too much fish.

This morning I found one very weak Threadfin Rainbow. I transferred him to my 10 gallon tank where I am keeping 5 Zebra Danios (originally 6 but one died). The 10 gallon was originally my quarantine tank. I had read that Danios are suitable in a peaceful community, as long as they are in groups - minimum 5, compatible with Threadfin Rainbows and do not bite other species. I thought that by transferring my Threadfin, he could get better if there weren't other Threadfin Rainbows to intimidate him.

When I got home from work, I found my poor Threadfin lying in the gravel with a 1/4 of his tail gone. I feel so terrible.

Can someone please explain to me what happened? Why he turned weak? And why the Zebra Danios ate him?

Also, why my 6th Zebra Danio died? The other Danios seem healthy and water conditions are fine (pH, temperature, nitrate, nitrite and ammonia checked)

I am considering ordering 2 female Threadfin Rainbows to counter the male aggression - is this the appropriate next step?

Finally, does this mean I should not integrate my Zebra Danios into my 20 gallon tank?

Thank you

 

[TropicalNorth]

If a fish is sick other fish will pick on it whatever the species, it's the whole survival thing. It's most likely the fish was stressed (or sick), the other fish then started picking on it which stressed it further and then it died. I don't think the zebra danios would have killed it, most likely they pecked at the fish after it died.

Rainbows don't do well in fairly new tanks, especially if its just cycled, I'm not sure why as the chemistry is usually fine. They do much better in mature tanks and threadfins are known for being more sensitive than other bows. Also a bit of aggression is okay, bows need to form a hierachy, but too much aggression is obviously a bad thing.

I would just keep an eye on them, don't add more fish and just see how it goes. If the threadfins do well for the next 2 weeks then most likely everything will be fine.

 

[Nolapete]

I don't think that Threadfins are actually a beginner fish and I surely wouldn't keep them in a tank that wasn't completely cycled. You will be hard pressed to find female threadfins as males have the beautiful fins that are desired. It's my understanding that breeders keep the females and sell off males for profit. The fish was probably already weak when you bought it. Stress and aggression exposed that weakness. I wouldn't keep threadfins with any other fish that stay in the same part of the water column as they do. The danios are going to be highly competitive with the threadfins for food in my opinion.

 

[indigofuse]

Okay, thank you both very much for your help.

- Will monitor tank conditions closely for 2 weeks
- Will not add any fish for 2 weeks or until all fish are thriving for at least 2 weeks (no deaths / sickenesses in that time)
- Will get another tank as quarantine tank

 

[Wat2Go]

[cycled my 20 gallon tank for 3 weeks.
Measurements taken yesterday are: pH = 7, temperature = 25, ammonia = 0, nitrite = 0.05, nitrate = 0]

The fact that you have no nitrate in your tank means it hasn't cycled completely.
I have been told that threadfin rainbows are rather delicate and even hard to keep in a very well established tank so maybe return the threadfins (the probably weren't cheap either) and pick something else?

Did you cycle the tank with the danios? They are very hardy but maybe the amonia or nitrite was too much?
I love danios but I have noticed they don't school well in a bigger tank and they are always rowdy and like to chase slower fish...

L.

 

[Dwarf Puffers]

You should have 0 Ammonia, o Trites, and over 5 trates. Threadfins are very delicate, and as mentioned, do better in established tanks. I would return them to your LFS and tell them to keep them (maybe a little pay to take care of the feeding) until you can get them. Take them back when you have 10 or so trates and 0 ammonia and trites.

I think you should get a tad bit larger tank, and try 3 males and your female, and only buy more when you find they're females. I'd say get a 40g or so, get 5 females and 3 males, and 10-12 danios...