Desperate for help with dying fish, lots of photos included

[harvester]

I've posted this on two other forums with no luck, so I'm hoping someone here can help. I've been keeping aquariums for 10 years, and this is my first major outbreak.

My tank's a 125g with a 55g bio-filter, a 30 gallon sump, and a Rena XP4 for mechanical filtration. Water quality's perfect - 80 degrees, pH 8.0, 0/0/<5 water stats, and hardness levels just right for cichlids.

I feed them a mix of cichlid excel, cichlid gold, and NLS cichlid pellets. The fish were all healthy when this started:

- 5 Acei (1.5-2.5 inches)
- 5 yellow lab (1.5-2 inches)
- 3 redfin hap (2-2.5 inches)
- 13 male hap/peacock (2-2.5 inches), which had been in the tank for a week

Here's how it started:

1. Flashing, which I thought was stress from the new fish.

2. The next day, two Acei turned dark and lethargic with pinkish/white patches on their top fin. I suspected parasites, specifically flukes.

I did a 50% water change, raised the temp to 85, and started a salt treatment. The next day, they looked worse - the patches had spread, and their scales were falling off in strings. They became more lethargic, lost their appetite, and swam weirdly.

I switched to Formalin and malachite green, suspecting fungus. I brought the temp back down in case it was bacteria. I did 25% water changes and daily treatments as directed.

On the third day, one of the sick Acei died. Most of its body had lost scales. The other one recovered, but with fin damage.

On the fourth day, three more fish developed the pinkish/white patches. I finished the treatment, but it seemed like it wasn't working.

The next day, my OB had black fins and spots, like spirulina poisoning. Two more fish died, and I euthanized them. The third recovered.

I suspected bacteria, so I ordered broad-spectrum antibiotics and parasite treatment. I'm still waiting for them.

Four days after the treatment, another fish developed the patches. I'm still doing 25% water changes daily.

The OB's black spots and fins went away, but I think it was a reaction to the malachite and Formalin. Two hours later, a hap developed the same black spots and fins. I think it's a reaction to chemicals or stress from water changes.

Last night, I noticed the inside of my rocks had turned bright mint green. Is this a reaction to the malachite?

Today, two more fish have the patches. The medicine I ordered is still on its way. Has anyone seen this before? It's killing my fish in 48 hours or leaving them scarred.

[kalevi]

I'm going to take a guess here - do any of your fish have a fuzzy growth around their mouths? I've been reading up on a disease that affects Malawis, it's called columnaris. If not treated quickly and correctly, it's usually fatal. I'm not entirely sure if that's what you're dealing with, but the symptoms in the 4th pic seem similar to columnaris. Those black dots on the Otopharynx, are they part of its natural colouring?

[harvester]

The middle fish in the last pic, its fins never were black before, but they turned that way for about a day - now they're back to normal. It also had small black spots, but they don't show up well in the picture - similar to the OB. Both went back to their normal color after a day or two, but I'm not sure if it's related.

I'm starting to think it's columnaris at this point, and hoping the kanamycin will take care of it. However, it doesn't have the usual mouth fuzz or any fuzz for that matter.

I'm curious, has anyone else ever had their rocks turn mint green like that? This tank was previously a marine tank, and I'm using reef lighting, but I've never had issues with this setup in cichlid tanks as long as the substrate was dark and there was plenty of cover.