[smidoid]

MY LFS have now started doing their fish only tanks with Cu @ 5PPM - and have a small note about inverts and not mixing the water.

Strikes me that even if the fish is "fished" out into a net and not placed in quarantine, there's like to be sufficient copper in on the fish to wipe out sensitive inverts and small corals in smaller systems; or am I being alarmist?

[CSeaSee]

I think it's good to be alarmist... 1 ppb invert toxicity is nothing to sneeze at. And since you have no actual guarantees about the Cu level other than the store's note, you really have no idea about how much Cu is really in that water.

[smidoid]

That's something I hadn't thought about - how can they know for certain that they have 5ppm (presumably of CuSO4) unless they know the exact capacity of the system.

Yet another reason for quarantine!

[Ninong]

Originally Posted by smidoid

MY LFS have now started doing their fish only tanks with Cu @ 5PPM - and have a small note about inverts and not mixing the water.

Surely that's a typo, right? You can't possibly mean 5 ppm Cu. I imagine you mean 0.5 ppm Cu. Most fish cannot survive 5 ppm copper.

Strikes me that even if the fish is "fished" out into a net and not placed in quarantine, there's like to be sufficient copper in on the fish to wipe out sensitive inverts and small corals in smaller systems; or am I being alarmist?

Most shops that run copper in their fish-holding tanks, net the fish out of the tank but then they place it in a bag of water from that very same system. Assuming you are willing to purchase a fish that has been treated prophylactically with copper, you must be careful to acclimate it when you get home in such a way that you end up with all of the bag water being discarded and the final water in the bag, or other container, being 100% tank water before you place the fish in your quarantine tank or in your main aquarium. And then you net it out of that final container.

Personally, I won't buy fish that have been kept in systems that run copper all the time. You have no way of knowing how long the fish have been exposed to this copper treatment. Copper is detrimental to the health of all fish, even at low therapeutic dosages. BTW, the recommended dosage to treat fish for Cryptocaryon irritans is 0.4-0.5 ppm. Copper damages the immune system and it can affect the reproductive system.

Even some experts in the hobby, like Scott Michael, for instance, who used to recommend copper, no longer do. He has written in his latest books that he now believes the harm done by copper exceeds the benefits and he doesn't recommend it for any purposes. There are alternatives, such as hyposalinity for ich.

P.S. -- The recommended dosage of copper can vary from product to product. Seachem, for example, recommends 0.5 ppm as the correct dosage for Cupramine.

[smidoid]

I expect it the 5ppm was a typo (or perhaps my memory!) but they are using it as a prophylactic; at least, that's what they are saying so I would imagine that it's 0.5. ;-)

I don't and won't use copper - especially after that warning because as I've said in other posts, my love is for inverts (and, in all honest, stuff that you need a small microscope to see). I'm making a QT while the system cycles and it will be ready well in time for the first fish.

I would have thought that dosing accurately in such a large system must be difficult to impossible. It seems like an odd claim. You are right that they bag the fish in the Cu "treated" water - hence the waring not to use it in the final system.

Now here's the killer: unless you test for Cu every time you re-dose, how on earth do you know how much CuSO4 is already in the system? Some will get lost during water changes, other amounts with bagging fish. Seems to me the more I think on this that there are too many variables.

Practically, in particular with those comments from Scott, it seems that we're actually best avoiding getting livestock from shops that actually use copper as a prophylactic.

Thank you for that extra information.