Aquatics Unlimited: Articles: Stocking the Marine Fish Aquarium
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Stocking the Marine Fish Aquarium

for the week of 2/26/98

Most people in the aquarium hobby know how quick and easy it is to stock a freshwater aquarium. The aquarium is set up, the water circulates for one or two days, and the first fish are added (generally about 1\4 of the total population). Four to six weeks later, after the nitrite cycle is completed, another batch of fish is added, followed by another and the tank is near full stock in the first couple of months that it is set up. The fish usually remain happy and healthy provided the aquarist is feeding carefully (not overfeeding) and doing water changes with regularity.

If this same stocking method is used on a marine aquarium, disaster could result. While freshwater fish can usually tolerate the small, temporary rises in ammonia and nitrite that follow any increase in stock, marine fish are much more sensitive. For one thing, the higher pH of the water (usually around 8.0-8.3 vs. 7.2-7.6 in the freshwater aquarium) makes ammonia much more toxic. In addition, saltwater fish actually "drink" seawater, which brings more toxic chemicals into their bodies.

A safer method:

After having the aquarium set up for 2 days (this allows for the salt and trace elements to dissolve and temperature to stabilize) the first few hardy fish may be added (usually damsels or black mollies). After the four to six week "break-in" cycle the first of the more exotic fish may be added. This first addition should only be one larger or two smaller fish. A period of two weeks to a month should be given to allow the bacteria culture to "catch up" to the waste put out by the tank's new inhabitants. If the bacteria are not allowed to multiply to the point that they can consume all the waste put out by the new fish the ammonia and or nitrite can skyrocket and weaken or kill all of the tanks inhabitants. This can be both costly and frustrating and is a major cause of people giving up the saltwater hobby.

The size of the new fish should also contribute to the amount of time one should wait between additions of fish. The addition of a 3" Naso Tang contributes very little to the bio-load of the aquarium in comparison to a 9" Naso Tang - probably about 1/27th. Therefore if a small fish is added the aquarist should wait 2 weeks before adding another fish, but if the 9" Tang is added, my best recommendation would be to wait at least a month before the next addition.

On a final note, maximum population density in the marine fish aquarium should not exceed 1\2" of fish per gallon of water. If this rule is observed and patience is exercised in adding fish to the aquarium, one should be very successful in the saltwater fish hobby.

Submitted by: Bruce Boziel

"Tip of the week" appeared regularly in 1999 and 2000.

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