Posted by TFH Magazine in Tropical Fish Hobbyist Blog on March 2, 2012 at 12:52 pm
Jay F. Hemdal
In the March and April 2012 issues of TFH I discussed basic and advanced acclimation techniques. One question that I did not address, but one that commonly comes up in discussions, is whether or not to dump the bag water into the fish tank. Since I was a child, I was always taught never allow any of a fish’s transport water to enter the aquarium during acclimation. The idea that this shipping water is polluted with both organic wastes and fish parasites is common knowledge to everyone, isn’t it? Knowing this to be true, I parroted that advice to thousands of people during my subsequent career in the pet trade and public aquariums. I never thought much about it, it became dogma for me.
What is the truth though? Certainly, animals produce waste, and while they are contained in a shipping bag, these wastes do build up. However, the amount the fish produces is relative to the shipping time, and if they had been in the operating aquarium for that same time, they would have produced the same amount of waste, yet the biological filter would have dealt with it in short order. If the addition this shipping water, with even an extra day’s build-up of wastes would harm the aquarium, then that system has much bigger problems with its biological filtration system that needs to be corrected.
What about the potential for disease introduction? Since the fish is being moved into the tank, it will be carrying any parasites with it anyway, so this is not as big of an issue as one might think. There is one theory though, that promotes the idea that during shipping, many parasites may become dislodged from their host fish, and that by adding shipping water to the tank you are in effect, adding extra parasites. The issue with this is that it has not been microscopically substantiated, nor is there any proof that such dislodged parasites can return and reinfect fish. Finally, if the fish had an infection, it is impossible that all parasites were dislodged into the shipping water, so the fish will still need to be medicated.
There are only two valid concerns regarding not adding shipping water to the aquarium: First, if the fish had been shipped with chemicals added to the water (including copper, methylene blue, or antibiotics) and secondly, the possibility that the water contains higher than normal levels of heterotrophic bacteria. Neither of these are major issues, especially since the first step of the acclimation process outlined here is to remove most of the original shipping water before the process begins.
Go ahead and let the small original volume of shipping water to return to the aquarium. You can then recover all of the tank water you added during additions, plus it is easier to just slide the fish out of the plastic bag. Most of us have had this happen: you struggle to net a fish out of the shipping bag, and you fumble for it as the fish flips out and hits the floor. Fish can be injured by net frames or caught in the net material itself. Some aquarists advocate transferring the fish by hand, but don’t try that with a rabbitfish or some other venomous species! Human hands are not adept at holding struggling fish, so in the end, it may be best to just tip the bag over and slide them out, water and all!
Photograph by AISPIX/Shutterstock