Hi all,

I have recently came accross my first ever cases of white spot and swim bladder problems, and now I have questions about medicating fish in general.

If one fish has it, is it best to treat all of them?
For parasites the answer I believe is yes, and they can stay in the tank, so we need to treat the whole tank all at once, but what about a swim bladder or other bacterial infections, logic dictates that the poorly fish could give the bacteria to the other fish in the tank doesn't it? Fungal infections, fin rot? Water is a very easy media to transmit diseases, generally, when is it recommended to isolate the poorly fish and when is it recommended to treat the whole tank?

What if your diagnosis was incorrect?
I have a case of whitespot which doesn't want to go away, either because the medication I'm using is not good, or perhaps its not whitespot, but velvet? What if its a combination of things, and my fish's immune system is so bad the medication is not enough to help? How long to wait before abandoning 1 medication to use another? How to change the fish's medication and avoid mixing the unknown chemicals in their water?
Can we just go straight in with the next meds or should we just leave the fish for a couple of days before putting them through the next set of treatment?

What about the filter bacteria and the carbon filters?
When medicating, we are to remove the carbon filters, but if good bacteria lives in the filters, won't removing some of the filter media crash your cycle? Should you keep your removed carbon filters in aquarium water that you aerate, and add some ammonia so your bacteria can eat? For BIORB tanks, the carbon is like little pellets, if 2 or 3 little carbon pellets stay in, does it matter? Which medications generally don't harm bacteria? - I'd have to assume, antibacterial medications such as swim bladder treatments, would harm the filters, in which case how do you keep your fish's water well, if you can't do water changes because of the meds. Just dose with Prime? Or is it better to do partial water changes and just re-medicate the fresh water you are adding? Both?

Can you use things like API stress coat to help reduce the stress in the fish while they are being medicated?
Or will that defeat the purpose in some cases as it coats their body and the meds now can't get in? My fish seem to have some sort of parasites and I am worried they will harm themselves - trying to rub against things, dashing around hitting tank walls, is there a way to reduce their stress or make them a little dopey?
Can you really be sure that adding anything else in their water while its medicated, (like stress coat or a second type of meds) will not cause unexpected chemical reactions, either making the medication less effective or straight up harmful?

To feed or not to feed?
Researching meds for my fish, most med suppliers say keep feeding them just smaller amounts, but usually the advice I get here, is to stop feeding them completely. How long can they go without food? Treatment of ick is 2 weeks. I believe this is most important in cases where the tank is not cycled or its an antibacterial treatment and hence the fish is in a tank with no biological filtration, so feeding the fish will cause water quality problems as well. What if you take the fish out, while you feed it? Doing partial water changes and re-medicating or dosing with prime would reduce the harmful substances in the water anyway, why not feed them a little? Of course don't feed if the meds say don't feed, for example with dropsy... Feeding garlic for example seems to be a bit of an old wives tale about parasites, and feeding peas helps constipation during swim bladder problems.. (the peas worked for my fish, so I believe in it)

Salts? Temperatures?

Lots of questions hopefully there will be lots of answers, I think it would be good to pin this or have 'Rules and Recommendations for Medicating Fish' article on this site.

Thank you!

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Generally, for any kind of parasite, we treat the whole tank. For bacterial infection, you can isolate the poorly fish if you have the facility, but it won't do any harm if you haven't the wherewithal to do that and treat the tank instead.
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Velvet and ich can be treated with the same medication and are distinguishable from each other. For a combination of things such as ich or velvet and bacterial or fungal infection, you can use Esha Exit and Esha 2000 at the same time (do not mix other manufacturers' meds though). When changing meds do a couple of large water changes and if possible run carbon for 24 hours between meds.
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Active carbon does not house bacteria so can safely be removed without affecting the cycle. Antibacterials, antifungals, and parasite treatments will usually not affect filter bacteria. The main culprit for affecting filtration is antibiotics, which are only available on vet prescription in the UK. Meth blue can also affect filter bacteria and should be used as a bath in a separate container, not a tank med.
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Stress coat and any slime coat stimulators including aloe vera will prevent meds from working. You should not mix meds except for the Esha products mentioned above which can be dosed in tandem.
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A good ich med takes 3 days treatment; most meds have a similar timescale. Feeding can be done sparingly if you wish, but most fish can go 2-3 weeks without food and suffer no harm.
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Don't mix salt and medication. Don't raise the temperature as it's unnecessary if using a decent medication and causes additional stress and oxygen deprivation. Be wary of salt with scaleless fish who cannot tolerate it.

A very helpful reply, Fishlady - not just for answering Lil2606's questions but also generally for any forum users. I've bought you a coffee by way of my own appreciation for this handy "go-to" guide. :)

Lil - if you ever have shrimp or snails, generally they can't tolerate the medication (the meds usually have a warning about this), which is where the hospital tank can come in handy. However, if it's a parasite, you then have a dilemma - if treating the main tank, the shrimp and snails may need to be re-housed permanently into a tank that's never had / will ever have medication in it.

Thanks for the coffee fcmf, and that's a good point about snails and shrimps. I think I'll see if I can pin this post in case it can help anyone else.