I have 6 Geophagus Altifrons which have been happy and healthy but where looking a bit thin, so I did a water change as per normal last Saturday and thought I might do a treatment for worms just to be safe. Anyway tonight I come home from work and all of the Geos are doing weird shit all over the show, vibration, flashing on the sand and driftwood staying still on the bottom. Some also have some welts on their skin not sores but like a lump.

I tested the water and found my water was 0.25 ammonia,  0 nitrites but nitrates are quite high like over 40. 

I have done another water change to try and sort the ammonia and nitrates. Other fish in the tank seem fine. One good thing is the fish aren't looking washed out and still showing colour. 

Would the worm treatment be something that could cause this? 

The worm treatment may have killed other organisms in the tank which in turn has caused the ammonia spike.

Or the dead worms could have caused it.

50% waterchange, keep monitoring nitrogen levels - expect a rise in nitrite as ammonia comes down. How often are you doing waterchanges? What is the volume of the tank and what is the stocking level? What filter?

I have done worm treatments on my cichlids and they do flash occasionally but they never get welts. More likely to be the ammonia burn. Need to bring down that nitrate level, I believe nitrates may be linked to HLE disease.

Tank is 480ltrs I will be doing water changes daily now that this is happening. Stock is 6 Geos 1 convict 7 small dither fish and a bristlenose. Largest Geo is close to 15cm and I will need to thin the heard once they are bigger. Tank has been running for almost two years no issues. Filter is Eheim classic 2 supposed to be good for 600ltrs.

I would just monitor the nitrogen levels and wait for things to stabilise. Ammonia/nitrite tend to be the issues.

Did a test this morning ammonia seems to slightly lower, nitrites still at 0 or maybe just higher, Nitrates are still high but are below 40 now.

Good news all of the Geos are doing well now all of the welts have gone down, water is better than before but still not perfect. The only thing I can put it down to is the wormer?? 

2 hours ago, Tread50 said:

Good news all of the Geos are doing well now all of the welts have gone down, water is better than before but still not perfect. The only thing I can put it down to is the wormer?? 

I've also used HFF's Praziquantel-based wormer as well as Flubendazole-based Kusuri wormer, but without experiencing issues like yours.

Good to know the Geos are now doing well.