Fin rot -- Achondrostoma oligolepis (cyprinid)

[agoncalves]

Hello all,

I have a 120 l, 31.7 gal aquarium with native species from the Iberian Peninsula. The aquarium has shrimps and snails, as well as several abundant plants. It has 3 species of fishes: Cobitis paludica, Gobio lozanoi (bottom feeders), Squalius alburnoides and Achondrostoma oligolepis. The first 3 are all immature and small fishes, around 3 cm, but the A. oligolepis are a bit bigger (around 7 cm, the adults may reach well above 15 cm). I have 15 fishes in total.
Three days ago a friend gave me the A. oligolepis I'm mentioning and I put them directly in the aquarium. He collected them from a nearby river. It was a mistake because I didn't notice the very, very small white patches of white in the tip of the fins. I did notice a tiny bit of a fin being "eaten" but it was so small I just assumed a predator did it.
One of the fishes got very sick overnight and the tail fin started to rot away. Yesterday, I went to a specialized store in fishes and they told me to use sera Phyto med Baktazid. I did as specified but this particular fish is becoming more and more ill as the sickness is destroying its fin quite fast (almost gone now) and spreading to the body (turning redish and scales rotting away).
I did put the very sick fish in a smaller aquarium in the same day I noticed it was sick.
The remaining fishes I kept in the main aquarium (I don't have space in the smaller one and no other options for now).

The disease is spreading much slower in those fishes, being barely visible (white spots almost indistinguible) but its cleary there, waiting to rot all away... Cobitis, Gobio and Squalius show no physical symptoms.

So, I wanted to separate these sick fishes but I can't do it until a get a new aquarium, which may take a few days. But should I do it or should it I try to treat all of them in the main aquarium where they are? I imagine the disease is already present in them all.
Should I try a different medication, bearing in mind the presence of invertebrates, etc? Alternatively, could I put the fishes aside and try with a stronger medication there?
I might be wrong but I don't think baktazid is doing the trick. Should I remove all of the water (I removed 25% before adding the baktazid and cleaned the sand with a syphon) and wash the rocks, etc? I am not very inclined to it because I don't want to disturbe the inverts and plants but I will do it if it helps. I have been told that adding aquarium salt in a small ammount might kill the bacteria but I don't know how much and I'm afraid it may kill the smaller fish or plants.

And regarding the sickest fish, do you recommend any actions to stop the spreading of the bacteria?

I'm trying to keep everything very clean and well oxigenated (I have a 550 l/h air pump and abundant plants). However, I wasn't able to check for ammonia yet (the store is close until monday).

I clearly did a lot of wrong things, including not having a proper extra aquarium to put fishes when they first arrive as tests for the water., and I'm lost..but I hope I can save the fishes.

Thank you in advance for any help and going thru all the text.

[Carl]

Hi & welcome to Everything Aquatic!

First, it is important to know all your parameters, including GH & KH

This short article covers this well, as often even the best medication will fail if certain aspects of aquarium care are missed:
www.aquarium-pond-answers.com/2016/09/how-to-treat-sick-fish.html

I do not know the natural biotope of the Iberian Peninsula (Spain, Portugal, etc.), but certain principles such as mineral Cations holds true for all fish.

Definitely a Fish bath with sodium chloride, Epsom salts, MethyBlu should be performed, as well as a direct application/swab of the infected arrea with AAP Wound Control/Merbromin

Further Reading:
www.aquarium-pond-answers.com/2009/07/fish-baths.html

Since it is spreading if I read correctly, albeit slowly, you are probably best treating the main aquarium.
I am not familiar with the ingredients in the medication you are using, so I cannot comment on it.

My Suggestion would be AAP Spectrogram
www.americanaquariumproducts.com/Aquatronics.html#spectrogram

Any pictures along with parameters would be helpful

Carl

[devonjohnsgard]

Agree with Carl that making sure water is under control, which includes KH and GH first, otherwise the treatment may not be as successful or the issue could reoccur. There is differences between rivers and aquariums, which is why KH and GH is important.

The articles Carl gave are good ones...

[agoncalves]

Thank you a lot!
I shall get those parameters tested and I will come back here. I will also try what you suggested Carl.I hope the fish bath helps it. This is a picture of it, showing the damage made by the bacteria already spreading into its body. The orange colours are typical for this spp.

[agoncalves]

I added the picture to the main message

[Carl]

In looking at the infection; I would strongly suggest the dieect application of AAP Wound Control/Merbromin to the affected area

Source:
www.americanaquariumproducts.com/Aquatronics.html#wound

Carl

[agoncalves]

Sadly, this poor fish got too sick before I was able to help it...the remaining are stable.
I have now tested the water parameters (couldn't get a gh test) and the ph is high but the kh low. Ph is 8 and kh 3.
Should I use a alkaline buffer? I have one that is intended to raise the ph and kh..what should i do?
Regarding the other parameters:
Ammonia is 0 but nitrite is 0,1.., nitrate 10.
I must get "cleansing" bacteria? I just changed 25% of the water and cleaned the sand. Maybe the filter could be better or I overfed the fish..

Once I fix the kh, I can try the medication again but before it won't work, right?

Also, I will get the gh test and maybe I could also get some other(s) which are important for plants. What should I get?


Thank you so much for all the help

[devonjohnsgard]

8 pH isnt bad. I would just keep it stable with a KH of 3-5. You could just a bit of alkaline buffer to get it up to 4 or 5 to help with pH swings between water changes.

GH and KH tests are most important in my option. Your KH isn't horrible. So, you could consider another treatment I would just make sure your dosing GH electrolytes at the same time.

[Carl]

I must get "cleansing" bacteria? I just changed 25% of the water and cleaned the sand. Maybe the filter could be better or I overfed the fish..

Be careful about cleaning sand, it can cause issues with your aquarium nitrogen cycle

Reference:
www.americanaquariumproducts.com/Aquarium_cleaning.html

The GH test is definitely a must, with the KH test almost as important.

As Devon noted, nothing needs to be added for KH at this time based on pH
Definitely make sure mineral Cations are being supplied while treating.

Knowing the ingredients of the product you are using might be helpful too

Carl