Maracyn and Maracyn-Two contains a broad spectrum antibiotic. The manufacturer claims that "when used as directed, they do not interfere with the biological filter", but you may want to take extra precautions. If they recommend a hospital tank in the instructions you should give this serious consideration.

I'd take that manufacturer's claim with a pound of salt, and I have to say that I agree with Keith here. You should consider treating your tank with antibiotics an absolute last resort (I'll explain at the end). Aside from the obvious fact that it could have serious ramifications for your biological filtration, probably many of your reef critters are dependent on a constant large supply of bacteria for their food (and in general indiscriminate use of antibiotics is a whole moral/medical issue, which I'll get to at the end of this message). If you cannot remove the fish from the aquarium, which sounds like the case here, I would suggest that you try Tetra's MarinOomed. It is the only medication I have ever used in my reef tank (or my FO tank for that matter), and it has proven effective for me in treating a variety of ectoparasitic and ecofungal infections. Since it does not contain any antibiotics, it has much less impact on the healthy function of your aquarium, provided you follow the directions.

*Important* One thing worthy of note for this medication, however, is that the primary active ingredient is Quinine hydrochloride, and despite the instructions to dose invertebrate tanks without corals at some intermediate amount between FO tanks and reef tanks, I would recommend you treat any molluscs in the tank (snails, clams, etc.) as corals for the purpose of their instructions. IME molluscs are far more sensitive to this medication than are the corals....

By the way is there a maracyn for saltwater or is the same I use for fresh.

No, there are different versions of the Mardel products - a freshwater and a saltwater line. Again, though, I would recommend against using them in your reef tank.

Treat the tank with Myacin.250mg.per 30 gal.every other day for 3 treatments.Remove poly filter and chemi-pure or carbon.turn skimmer way down.This will stop spreading of fungus and take care of it on psuedochromis.treat tank with phosphate remover afterwards.

This recommended treatment falls into the "indiscrimate use of antibiotics" category. What follows is a *gross* oversimplification of the processes involved, but it gets the idea across....

Antibiotics function in a wide variety of mechanisms, but most generally slow down reproduction by interfering with some cellular process (e.g., cell wall , or microtubule formation, etc.) -- that means that the bacteria are still growing, just slowly enough that the immune system of the fishes is capable of dealing with the pathogen faster than the pathogen can reproduce. This is the "normal" state of affairs, and when pathogens are in low concentration within the body, the immune system mobilizes to destroy them. If for some reason the pathogen gets a head start, they can reproduce faster than the local immune system can deal with them (an infection). In most cases the immune system can draw on resources from other areas of the body to deal with the infection and it can be stopped, but once the infection gets rolling, most pathogens can reproduce faster than the immune system cells, and they can run rampant in the host. The idea of using antibiotics is to mess with the reproductive cycle of the pathogen enough that the table is turned and the host immune system becomes the more efficient of the two. In general antibiotic doses are calculated such that reproduction is slowed to the point where the pathogen dies before it is able to complete its life cycle and the treatment last long enough that those individuals that manage to survive are eradicated by the host immune system. That's why your doctor (should!) alway give you enough antibiotic to last well into when you're feeling better, and why you should always take your prescription until it's finished rather than quit taking the pills when you feel better.

The problems with dosing your tank with antibiotics are:

• There are a variety of mutations occurring all the time during the normal background reproduction, most of those mutations will be slightly to greatly disadvantageous to the individual, and they will disappear. But some of those apparently disadvantageous mutations can become a huge advantage when in the presence of antibiotics, because the pathogen with that mutation may be unaffected by it (for example, the pathogen uses a slightly less efficient, but still functional pathway or product to accomplish the same goal). In this case, the pathogen continues to reproduce at the normal rate (or close to it) in the presence of the antibiotic you've used in an attempt to turn the tables (this is known as antibiotic resistence) and the infection proceeds unimpeded (and therefore that antibiotic is basically useless). This is a normal problem and a risk of any antibiotic use, regardless of the application, although if the application is rare enough and the cost of antibiotic resistence is high enough the anitobiotic retains its usefulness because the antibiotic resistent bacteria are outcompeted by their non-resistent relatives between rare bouts of antibiotic application. As soon as an antibiotic becomes widely available and widely used (e.g., pretty much anything available in a petshop), the advantage to the pathogen of carrying the genes for antibiotic resistence generally outweigh the costs of not having them, and antibiotic resistence becomes widespread.
• The more insiduous problem with antibiotic treatment is when following advice such as that above. The bacteria are generally still alive during the treatment (remember antibiotics don't kill the bacteria, they mess with their reproduction), and if the dose is low enough, they can continue to reproduce (albeit very slowly) throughout the treatment. Although this is likely to have the effect that you desire (the tables are turned and the fish gets better), the pathogen is able to continue reproduction (the outcome of which is genetic recombination, which provides a variety of different genetic makeups to be "tested" against the antibiotic), and those that are most successful survive because the treatment dosage is low, and it is only continued for a short period of time (the host immune system doesn't have time to mop up all of the surviving pathogen before reproduction comes back to normal). If a particular recombination does better in the presence of that antibiotic than the rest of the bacteria, it will produce more "offspring" than the rest, and because those individuals are more common, it is more likely that those will be the individuals left behind when the antibiotic treatment is stopped. The end result? That antibiotic will be less effective the next time that pathogen invades a host. By treating with below average doses of antibiotics and for decreased amounts of time, you increase the likelihood of these "bad" outcomes.

If antibiotic treatment proves necessary, I would certainly not discourage you from trying to save the fish, but please treat with antibiotics responsibly. Get the fish into a hospital tank, treat at the full dose for the full amount of time, and when you are finished, boil the hosiptal tank water and treat the boiled water with bleach to ensure that you kill any remaining bacteria and completely denature any antibiotics added to the tank before you dispose of it. You'll be doing yourself and everyone else a big favor.

Just my $0.02