Are there any side effects to dosing a tank with 2mg/L of praziquantel? I've read that discus keepers regularly deworm their fish. I'm assuming this is what they use? Is there reason to worry about biological filtration after dosing? Anything else worth mentioning?

Other than the rare allergic or anaphalactic reactions, there are no significant side effects for praziquantel, even at several times the dose rate although the action of the drug is dependent on it being metabolized by the liver so if this organ system is already compromised, the drug could exacerbate the condition. There is no risk to your tank.

I think the biggest risk is with developing drug resistance so careful use and dosing is important. Theoretically, you should not need to keep redosing once you have treated an animal unless the animal is repeatedly exposed to new populations of the parasitic organism.

Other than the rare allergic or anaphalactic reactions, there are no significant side effects for praziquantel, even at several times the dose rate although the action of the drug is dependent on it being metabolized by the liver so if this organ system is already compromised, the drug could exacerbate the condition. There is no risk to your tank.

I think the biggest risk is with developing drug resistance so careful use and dosing is important. Theoretically, you should not need to keep redosing once you have treated an animal unless the animal is repeatedly exposed to new populations of the parasitic organism.

Thanks for that Jennifer. I have a feeling the first time I dosed my blue rams with praziquantel a few months ago it wasn't actually prazi (bought from pet shop fish keepers "private stash") because I bought some more the other day and it looks completely different. As well as being individually blister packed.

Praziquantel is marketed under a few different trade names so I would not be surprised if it looked different...however, mysteriously packaged secret drugs sound somewhat questionable!

Keep in mind, praziquantel will not kill the most common worms, like roundworms. It will kill cestodes and trematodes (flukes and tapeworms) though.

I'm pretty sure they have gill flukes . Continuously scraping against tank objects around the gill area.

Well hopefully the praziquantel will do the job. It should immobilise the flukes fairly soon after dosing but the gills may still be inflammed for a week or so afterward so the symptoms may persist for a few days.