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Dwarf Cichlid Picking on Corydoras


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Everything was going so well!

40 gallon tank, newly planted stocked with 12 black neons, 12 panda corydoras, 1 young bristlenose catfish, and 2 dwarf cichlids (Nannacara anomala).   We added the cichlid pair last week and watched them like a hawk.  The male chases the female a bit, but I set up the tank with a pair of SA cichlids in mind.  So there's lots of little nooks and crannies for hiding and hanging out even though the plants haven't really filled in yet.

But we noticed that 3 of the corydoras (so far it's just the 3 as far as we can tell) have chunks missing out of their tails.  They look fine otherwise, and the parameters seem fine (although the KH is very low), so I'm guessing it has to be Bob.  We've seen him chase a couple corys off from a spot from time to time, but haven't actually witnessed him nipping them.

So, I have a few options.  What would you do?

1. Move all of the corys to my son's 29 gallon.   (He loves that idea).  I'm hesitant because that tank is so young.

2. Move the affected corys to a qt. tank to be sure that this is a case of fin nipping and not a disease process.   This will allow me to help them out with an meds necessary to promote healing.

3. Move all of the corys to a qt. tank until the 29 gallon is ready for them and treat all of them even if there's been no fin nipping.  I'll just have to go out and buy a bigger qt tank.

4. Remove the cichlids.  I don't have a suitable tank for them long term.  We don't want them in the kiddo's 29.

5. Watch and see.  The only reason I'm suggesting this is because I wonder if the corys will learn to avoid Bob.  But this seems like the more stressful solution for both myself and the cory school.

5a. Add some more plants stat and then watch and see.

Agh!  Option 3 seems the most reasonable and responsible but I would like it to be as simple as 5a.  I'm happy to get some input.  I've never really dealt with trauma or disease in a tank before.   I've been pretty lucky.  I feel like I should have enough experience that I shouldn't be all aflutter like this.


Ammonia = 0 (API Ammonia test)

Nitrite = 0 (Tetra easy strips)

Nitrate = around 20 (Tetra easy strips)

GH - 25><75 (Tetra easy strips)

KH - <40 (honestly, looks like 0 on the strip) (Tetra easy strips)

pH - 6.8 or thereabouts 






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When I have had instances where some of my fish just didn't seem to get along with others, I have always opted to put them in a separate tank, let them relax and heal for a bit, then I generally try to place them in a different tank with a different group. But that is because I am a big softy and I hate to see any of my tanks stressed, rather than because I am certain it is really necessary. Petco is having their dollar a gallon sale right now...just saying....if you have one near you... 🙂

I have a really bully-ish Dwarf Gourami that I originally had issues with as he was chasing my Tetras around. I pulled him out, added a few Water Sprite to create some heavier bushes in the back corner, rearranged the other plants a bit to break up the viewing area from within the tank side to side, and put him back in the tank. I assumed the Tetra would appreciate the place to hide. I was surprised when my Gourami took over the bushy corner, but left everyone alone after that. Turns out, he just wanted his own little green nook. Also, I think re-adding him to the tank as kind of the new kid, with a different layout, calmed him down somewhat. 

Full disclosure, I don't know very much about Cichlids. But for what its worth, I would either take the Corys out and QT them (just observation first, then meds if needed), before moving them into your son's 29 gallon, or I would temporarily remove the Cichlids, add more plants that break up the viewing area within the tank (not blocking your view from the front of course), shake up the rest of the plants and decor a bit, then put the Cichlids back in to see if that helps. 😉

How big is your QT tank? I once had 15 Panda Corys, alone, in a 10 gallon planted tank for about a month. I am not proud, but I unexpectedly inherited them. I put a bigger cycled filter on the tank (swapped with an established tank with 2 filters on it) and was more diligent about watching the parameters and detritus build up. I was concerned because they liked to dog pile on each other in a corner of that tank and I thought it was a reaction to the tank size. (I hadn't had any Corys prior to that.) Now they are in a 40 gallon and still like to dog pile on each other at night. Everything turned out great! I think if you are diligent about keeping an eye on the parameters, they could be alright in a small-ish tank short term. But I wouldn't attempt anything smaller than a 10 gallon.  

P.S. I have lots of experience with diseased and trauma affected fish (I am a sucker for fish who look rough and need some TLC), but it still stresses me out when any of my little guys or gals are sick or are being bullied. I would be more concerned if you didn't care that your fish are missing chunks from their tails. 🙂 


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Thanks!  We talked more here at home tonight and are going to move the gang to a 10 gallon quarantine tank (yes, a trip to Petco will be happening first thing tomorrow. ). Then once we are certain that it's ready, we will move them to the 29. 

I don't want to though.  But it's not like I can force everyone to get along. 

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