When I bought him, the LFS said they thought it was not a tank-raised clown because their costs were cheaper than the normal tank-raised they got. Maybe I made a mistake by taking him because out of the 5 in that shipment, he was the only one to make it. They had him for over a week and was eating, so I figured I was safe.
Well, lesson learned (and encourage them to carry tank-bred and raised animals
whenever they can, PLEASE!). As a matter of fact, when you consider the dead rate of those 'cheaper' clowns.. hhmm.. I don't know how they do their figuring. In any event.. This is also the reason for quarantining EVERYTHING that's going into a display.
Do some water changes. You listed no invertebrates or other animals that need to take up calcium, so in my opinion that's an unnecessary test. Again, water changes are all that these animals need at most. If you're mixing your own water, test
it, too, and if possible try to get the water district's latest test results (it can be surprising what's allowed to be in potable water!). Just remember, we can only test for a very few components, that in no way provides the total picture of what an animal needs.
One thing, do be sure to have a hospital tank/container set up and ready to go. Lympho doesn't normally spread quickly, slow to grow and slow to go.
I do prefer Selcon, but there are those who use Marine Zoe with acceptable results. What strengthened my stand on Selcon was seeing it used at the Long Beach Aquarium of the Pacific (for the otters and seals, even!). The aquarists there consider it the best stuff for most purposes.