Uhh, Jimbo - for marine animals, no filter, no life.
Unless you mean no mechanical or chemical filtration.
That's all crap anyway.
For a hospital tank, set it up with live rock, skimmer and everything else a regular tank needs. Then hang on a 25 - 100 watt UV sterilizer. That does away with the need for chemicals, which generally do more harm than good.
I stopped using chemicals years ago. For fresh and salt.
A strong UV sterilizer kills pathogens. Chemicals and antibiotics kill the pathogens AND the livestock.
I can't believe I'm the only one out there preaching this message. Since I'm not all that smart, it must be because I don't make a profit from selling chemicals and antibiotics.
HOWEVER: Sometimes, antibiotics must be used IF you are certain of the pathogen affecting your livestock. But for prophylactic, (I.E. a quarantine tank) a UV is the best choice. If you use a bare-bottom hospital tank, you’d better do daily water changes, and watch water parameters closely.
BTW- If you don’t use a quarantine tank, you’re going to kill a lot of livestock - needlessly.