Disaster strikes!?
It was a rough weekend for our trout. When I went in to check on them Saturday, I found this…
One of many dead this weekend...
…and about 19 more like him! I immediately checked the tank equipment. Seems the artificial filter system had air in the line, and had quit removing wastes and decreased flow in the tank. I quickly primed the pump on the filter, and water started moving again. I sucked the dead trout out of the tank, so their decomposing bodies would not add to the nitrogen spike surely going on in the tank. I immediately changed 5% of the water with fresh water I had on hand. I decided to avoid adding much food for the day also.
When I came in today (Sunday), I found 25 more dead trout! So, if we had an estimated 150 fry at the start of the month then we have lost about 50 total–about 30%! Is that a high mortality rate? I’m not sure since this is my first time managing trout in a 55 gallon aquarium. In the wild, trout (and many fish) have evolved in fast moving streams with little food and numerous predators so they lay hundreds to thousands of eggs–many which do not survive. So, trout experience high mortality rates in the wild.
We’re trying to maintain a simple artificial habitat for these trout, and my students are trying to maintain more complex ones called ecocolumns. These columns have two terrariums and one aquarium built using 2 liter bottles:
Artificial Ecosystems
We’ve all experienced a similar phenomenon now–a nitrogen spike. As the living things in the tank feed and produce waste ammonia, the bacteria in the water (and soil in their terrestrial chambers) convert it to nitrites and nitrates. While plants thrive on nitrates, animals find these nitrogen-rich compounds toxic. The range of tolerance for living things is often not very wide, and trout are especially fragile fish. So, I verified the spike was ammonia (instead of nitrates) and quickly did a 15-20% water change to get the stuff out of the water. I also cut back on food again, as decomposing uneaten food can also “feed” the nitrogen cycle.
Perhaps all will be ok. I’m not sure just how many trout we can sustain in a 55 gallon tank long term.
