Originally published on Goldfish Connection’s website, “Topics of Interest”  www.goldfishconnection.com/

“U. V. in the Goldfish Tank”

By: Rick G. Copeland

Recently I’ve seen a wave of concerns and questions about using Ultra Violet (U.V.) sterilizers in goldfish aquariums.  This seems to be an age-old debate that resurfaces periodically.  For some years now koi keepers have been using U.V. with great success in their koi ponds.  U.V. in a pond helps control green water as well as free-floating bacteria and parasites in the water.

So why as goldfish keepers are we hesitant?  The purpose of this article is to dispel some of the misconceptions and clarify the benefits of U.V.  And as you will see, the addition of a U.V. sterilizer can only benefit our valuable goldfish collections.

U.V. and Dechlorinating products don’t mix ??

To start let’s look at the dynamics of adding a dechlorinator (usually Sodium thiosulphate) to the aquarium while doing water changes.  As soon as the dechlorinator mixes with the water the chlorine is neutralized.  A U.V. with the proper flow rate cannot possibly counteract this process, as the chlorine is gone before it is passed through the U.V.  Also, there is no reaction producing toxic compounds when the Sodium Thiosulphate passes through a U.V. 

In the case of chloramine and ammonia bonding agents there is no reaction with the U.V. that unbinds the ammonia.  Since the bonding of ammonia is not as instantaneous as the neutralization of the chlorine it is prudent to pre-treat the new water prior to adding it to the aquarium.  This prevents the fish being exposed to the ammonia prior to it being bound by the bonding agent and also prevents the bonding agent from being neutralized in the water before all the ammonia is bound.

Using a U.V. will neutralize medications added to the water ??

For the most part this is true.  It is common practice to turn off U.V. when treating the water with medication.  Once treatment is complete the U.V. is turned back on to control free-floating bacteria and parasites.  This greatly reduces chances of re-infestation.

U.V. produces ozone when exposed to oxygen in the water ??

This is untrue with the germicidal type U.V. lamps used in U.V. sterilizers for aquarium water purification.  There are U.V. lamps that can produce ozone.  They have a pinpoint wavelength of 185.0 nanometers where 253.7 nanometers is the pinpoint of germicidal U.V.

U.V. will prevent the establishment of nitrifying bacteria ??

Nitrosomonas and Nitrobacter are not free-swimming bacteria therefore will not come in contact with the U.V.  They attach themselves to filtration media, gravel, the sides of the aquarium, etc.  The only way U.V. could effect the establishment of nitrifying bacteria is if a seed bacteria product is added to the water.  In this case it would be advisable to turn off the U.V. until the free-floating, nitrifying bacteria has had a chance to get a foothold.

U.V. will cause fish to lose their resistance to disease and parasites because they are living in a sterile environment ??

Because the sterilized water from the U.V. is returned to the tank mixing it with un-sterilized water there is no way to remove all bacteria and parasites in the water.  Without going into a discussion on purity coefficients suffice it to say that a properly sized U.V. with the correct flow rate will kill 99.99% of the bacterial pathogens and parasites that are in the water of the aquarium.  Additionally fish produce waste, along with this waste comes bacteria.  The U.V. is simply removing the disease factor in the water.  Many people equate this with the “boy in the bubble” syndrome.  The fish do not lose their immune system and the immune system does not go dormant.  The energy used to fight disease is redirected to growth and color.

U.V. only kills bacteria and not parasites ??

Untrue.  Parasites attached to the fish are of course not affected by the U.V.  When a parasite is in it’s free-swimming stage of its life cycle the U.V. then will eliminate it from the water.  So medication will need to be added to the tank to remove the parasites from the fish.  After that the U.V. will protect them from re-infestation.

A U.V. that will produce 28,000 microwatts with a contact time with the water of five seconds will kill the following parasites and bacterial pathogens found in the goldfish aquarium:

Chilodinella
Costia
Epistylis
Heximita
Ichthyophithirius Multifilis (freshwater Ich)
Trichodina
Flukes - Dactylogyrus and Gyrodactylus
Argulus
Lernea (Anchor worm)
Aeromonas - hydrophila, salmonicida

Certomyxa shasta
Edwardsiella - Septicemia
Flexibacter columinaris
Mycobacterium fortuitum – Tuberculosis
Pseudomonas - flourescens, putida, anguilliseptia, aeruginosa
Sacrina lutea
Saprolegenia hyphae

In summary, with U.V. sterilization we are creating a healthier environment for our goldfish.  In closed systems, like aquariums, bacterial pathogens and parasites can reproduce at alarming rates.  Controlling these bacterial pathogens and parasites with U.V. can not only eliminate disease outbreaks but also produce a much healthier environment in which our goldfish will thrive. 

References. 

Aquatic Systems Engineering, P.R. Escobal, Dimension Engineering Press, Oxnard, California

Rick Hess, Goldfish Connection, www.goldfishconnection.com

Rick Kinter, founder and President of Pure Water Products Inc., manufacturer of U.V. 1 sterilizers.

Copyright 2002 Rick G. Copeland