Decomposition Rate of Brine Shrimp Eggs

There has been some concern that extra hatched and un-hatched brine shrimp eggs that get into feedings of live brine shrimp will cause problems in the tank they are in.

These brine shrimp egg shells tend to accumulate along the top rim of tanks, and are readily drawn into sponge filters where they can accumulate in very large numbers. The theory is that they will be broken down by bacteria which in turn, will cause a couple problems in the tank. One assumption is that the increased ammonia and nitrites the bacteria produce, will not be readily handled by the bio-filter and will cause problems generally associated with high levels of ammonia and nitrites. The other problem would be the result of the large increase in these heterotrophic bacteria, which would attack the fish. This would possibly cause internal and/or finnage problems.

(2/13/01) After observing no problems from huge numbers of excess brine shrimp egg shells in the artemia shell experiment involving angelfish eating large numbers of these shells, I concluded that the cyst covering, decomposed very slowly. Today, I took the filter out of that test tank (test still in progress), and squeezed it out for the first time since that experiment started. The number of brine shrimp egg shells trapped in this filter was incredible. It appeared as if almost every shell that had been put in this tank during this test, ended up in the filter, without being decomposed. The fish at this point, still show no signs of a high bacteria load and the tank has zero ammonia and nitrite levels.

Test: I've decided to test the decomposition rate of several items. I will have each sample in it's own container. The items will be live newly hatched brine shrimp, fresh flake food, dried decapsulated brine shrimp egg cysts, previously hatched brine shrimp egg shells, and regular un-hatched brine shrimp egg cysts. They will be kept in a room that is approximately 85°. The pH is 8.2 and the water is moderately hard. These conditions will generally promote fast growth of heterotrophic bacteria. Observations will be made once each day and recorded.

One half cup of tank water was placed in 5 small plastic containers. As water evaporated, tank water was added to each container (twice a week). These were placed on a shelf, 24" from an overhead fluorescent light. A quarter teaspoon of each type of brine shrimp eggs was place in its own separate container. The live brine shrimp was the amount approximate to what would hatch from a quarter teaspoon of cysts. A single flake, 2" x 2" was put in the other container. I thought this size flake would approximate a quarter teaspoon of flake, if crushed.

7 Days Later

14 Days Later

30 Days Later

55 Days Later:

Conclusions: Live brine shrimp decomposed rapidly as expected. Most of the flake food decomposed almost as quickly, but a small amount of flake took a longer time to decompose than I expected. The clear inner shell that remains on decapsulated brine shrimp eggs, does not seem to decompose very quickly, but the material inside does seem to be readily affected. I'm guessing that the clear shell splits open, but the split is difficult to see on this clear layer. un-hatched brine shrimp eggs also exhibited a different reaction than I expected. The outer shell was completely unaffected, but after at least a few weeks, it appears that most of the shells split open and the decomposition of the internal material then takes place. Hatched brine shrimp egg shells showed no sign of decomposition. It is my belief that if no deterioration has taken place after 55 days, it is not a concern in the management of our aquariums.

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