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Old 03/29/2011, 12:55 PM   #1
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Join Date: Feb 2006
Location: Spokane WA
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Too Big a Tank/Fish for QT: What to do?

This is something that we need to deal with all too often.
First statement, and it has to be said: quarantine everything if you have a mega-tank. Treatment after the fact is a pita and risks the tank!

Ok, now we just say---"we've got a parasite or an infection and the fish are huge and the tank is 500 gallons---what do we do?"

#1 diagnose it accurately.
#2 consider removing certain species to a different treatment if needful. EG, mandarins need a cycled qt with pods but are very resistent to ich, etc. And if you have corals or nems, or inverts, get them out and plan to have them out for 8 weeks: after that time, any ich or parasite that moved with them will have died out. Bacteria are a little iffier, but I would not subject corals to an antibacterial. Their zooxanthellae are dinoflagellate-like, and corals are often attacked by gram-negative bacteria; but unless you're an expert, these factoids aren't going to help much. Preformulated dips are the best thing for corals. Whether these dips can blitz the bad bacteria I do not know: read your labels, and if they do, great, put them back in after treatment. If they don't, that's a problem you need to take up with a coral expert.
#3 consider reducing your fish load by treating certain species in separate tanks.
#4 hypo for parasites is about the only treatment that won't take out your tank, but it's going to be rough on your tank all the same. There are several ways to get through this.
a) Do NOT stress the tank: put everybody on a slight diet, no treats, have tangs eating as much green stuff as possible, as little protein as possible, and keep your skimmer tuned. If you have a punk skimmer, consider a better one.
b) maintain an absolutely rigid salinity and be sure you're spot-on all the time: an ATO is essential, ditto a well-calibrated refractometer.
c) follow the schedule, and examine ALL fish for any sign of disease with a magnifying glass, before you conclude you can now start the 4 week exit-countdown.

If you have to treat anything else, with antibiotic, try to withdraw that fish to qt to treat and cross your fingers for the rest.

If there ARE any fish diseases that are gram positive bacterial, you could use a gram positive antibiotic if the tank's life totally depended on it: your sandbed bacteria are gram negative. This is how ChemiClean operates: [it is a gram positive specific antibiotic, and cyanobacteria are gram positive, ergo it misses killing your sandbed: but the skimmer gets a huge overload from the dieoff.]. But be VERY careful with your diagnosis. And read, read, read. Never dose a gram negative type antibiotic or a broad spectrum antibiotic into your tank, or it will immediately take out your sandbed and live rock.

A uv filter MIGHT help if you have a gram negative infection like fin rot running rampant in your tank. But UV must be set up very precisely on a closed loop with a proper pump scaled to the filter.

If you are unsure whether a disease is parasitic or antibiotic, get several expert opinions off several VERY clear photos before doing anything involving antibiotics.
And remember that the person writing this is NOT a biologist nor a chemist. Check with several people and read up and be absolutely sure before doing anything with antibiotics!


Salinity 1.024-6; alkalinity 8.3-9.3 on KH scale; calcium 420; magnesium 1300, temp 78-80, nitrate .2. Ammonia 0. No filters: lps tank. Alk and cal won't rise if mg is low.

Current Tank Info: 105g AquaVim wedge, chromis, royal gramma basslet, tailspot blenny, ocellaris clown, yellow watchman, chestnut turbo snails, bristleworms, couple of hermits.

Last edited by Sk8r; 03/29/2011 at 01:18 PM.
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Old 09/15/2014, 05:32 PM   #2
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Join Date: Jun 2007
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The size of any fish or the total bioload of all fish for QT should never be an issue.

There are some practical considerations such as how to get temporary holding tanks big enough. Plastic containers, if inert or lined with inert plastic sheets, can do. They may have to be supported for lack of enough rigidity.

As an experienced aquarist, I always prefer to QT all the fish intended for a tank setup all at once. Newbies perhaps should not do so for lack of skills in handling diseases.

It is always easy to cycle enough medium well enough to handle any bioload, no matter how great, all at once.

When you put all your eggs in the same basket and watch it well with all your skills, and take some calculated chances for all the benefits, UV against bacterial and viral infection is necessary, IME.

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