Biodegradation - Are bacteria rendering your quarantine process useless?

Humblefish

Dr. Fish
HF Vendor
Location
Navarre, FL
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Biodegradation is the term given to the breakdown of organic chemicals by the biological action of a living organism.

How is this relevant to our aquariums and in particular, a quarantine tank (QT)? Every single medication you dose (EXCEPT COPPER) is susceptible to biodegradation. (Liquid copper is a poison, not a true medication.) What happens in any aquarium is bacteria (especially biofilm and heterotrophic bacteria) decomposes any medication it comes into contact with. How rapidly this occurs is usually directly related to how mature an aquarium is. This is why it is often very difficult to successfully use medications in a display tank (DT) environment with rock & sand which harbors tons of bacteria.

Biodegradation in a QT: To be clear, it is always optimal to dose medications in as sterile an environment as possible (meaning, no biofilter). However, this is often not practical due to ammonia produced by fish waste, uneaten food, etc. So the next best thing is to setup your QT with as little nitrifying bacteria as possible. (I.E. Don't overdose the bacteria in a bottle product you are using when setting up a QT.) Also keep in mind the longer a QT is set up, the less effective the medications you dose will be. Therefore, you will eventually need to sterilize and reseed your QT. How long? I would do it no less than every 3-4 months.

QT and Biofilm: A biofilm is any group of microorganisms which stick to each other and then adhere to a surface. Think bacteria sticking to the glass of a QT. It will look hazy and you won't be able to just rub it off using an algae pad. The only way to remove it is drain the tank, and use detergent, Isopropyl Rubbing Alcohol or possibly H2O2. Ideally you would find a fish-safe detergent followed by 20 min alcohol application. H2O2 would be a second choice, but bleach is no good in this situation.

How to sterilize + reseed any tank: Ideally, you would take the QT outside, wipe everything down using vinegar and then allow to thoroughly air dry (which sterilizes). If you encounter any "rough patches" (like biofilm) on the tank or equipment use one of chemicals mentioned above to remove it. A faster method (assuming no biofilm is present) is outlined below:
  1. Dose 100ppm chlorine as per this guide: https://dec.vermont.gov/sites/dec/files/dwgwp/DW/chlorinedosageemergencydisinfection.pdf
  2. Stir the sand and use a powerhead to blow inside any large rock to ensure the chlorinated water reaches every part of your tank.
  3. Circulate well for 48 hours, and then use sodium thiosulfate to neutralize the chlorine in the water. Most pool places sell a product called Chlor Out which contains sodium thiosulfate and is safe to use. You can use this website to determine how much sodium thiosulfate to dose: https://www.edspumps.com/water-treatment/documents/Antichlorination.pdf
  4. After you are all finished, your alkalinity might need to be raised. If so, use baking soda as per this calculator: http://reef.diesyst.com/chemcalc/chemcalc.html
  5. Dose nitrifying bacteria (products tested here and here) for at least 1 week in order to reseed.
P.S. I've also attached a spreadsheet you can use to determine all of the above.

Further reading:


 

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Rascal

Seeker of enlightenment
Location
Midland Texas
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Is there any advantage other than time and saltwater between the 2 methods in a bare bottom setup? I’m going to break my treatment tank down for cleaning after this round and honestly thinking about the vinegar application inside and out of everything.
 

Humblefish

Dr. Fish
HF Vendor
Thread starter
Location
Navarre, FL
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Is there any advantage other than time and saltwater between the 2 methods in a bare bottom setup? I’m going to break my treatment tank down for cleaning after this round and honestly thinking about the vinegar application inside and out of everything.

Breaking down & sterilizing your QT in-between every batch of fish is the optimal thing to do. Dosing chlorine and reseeding works too, BUT it will not eliminate biofilm so you are taking a chance of that being present on the glass or inside a filter.
 

AndyR83

Way better at fixing people than fish
Location
Northeast USA
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The timing of this article couldn’t be better! I was just wondering about something seemingly related to this, and you’ve answered a lot of the questions I was trying to figure out how to even ask.

Essentially, I find myself having to perform “rapid turnovers” of my quarantine tanks with extremely high frequency. Given the need to get the tanks and equipment sterilized and then promptly back into service, I always use bleach. Though these tanks are all in use almost perpetually, none of them are ever operating for more than a few consecutive days before getting the bleach treatment and starting over again with new saltwater.

I set this up as a “four bay” system, so two QT cohorts can always be running and they both always have a tank ready to swap into when the time is right. This means all four tanks get bleached about twice a week, then rinsed like crazy, refilled, and allowed to run for a day or two until the fish are transferred back over. Despitethe fact that these tanks get bleached more than most, I’ve begun to notice the sort of hazy, rough surfaces you mention in your description of biofilm. The water seems to become cloudy much faster in these tanks once livestock are added as well, compared to my display tanks. It certainly seems like the issues you’ve shared are at least partially to blame.

Is there any “rapid turnover” option that is able to address this effectively? If not, I suppose the best thing for me to do may be to have two additional tanksin the rotation to allow them some down time as they cycle through... though that may be a tough sell for me with my wife!
 
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