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The Sound of Science - 'Fish Tanks and Nitrogen Cycle'

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NIU STEM Outreach

Newt: You're listening to The Sound of Science on WNIJ. I'm Newt with NIU STEAM.

Becky: And I'm Becky. Have you ever noticed that your fish tank water looks cloudy even after a good cleaning?

Newt: I scrub the glass, refresh the water, and get all my plants in place. And it looks dirty again so quickly. Why is that?

Becky: Well Newt, that is because you disrupted the nitrogen cycle. Your tank is its own ecosystem that needs to maintain a balance. All fish tanks have a delicate combination of ammonia, nitrites and nitrates. We do need to clean our tanks to keep things hygienic, but changing the water or filter can upset this balance. If the combination is too far out of whack things can become toxic.

Newt: I know ammonia is a byproduct of digesting and expelling food. But what are nitrites and nitrates? Where do they come from?

Becky: Ammonia can also come from dead material, live plants, and uneaten food. This is the most toxic part of the nitrogen cycle, but that ammonia then turns into nitrites, which eventually become nitrates. Each step of the cycle decreases the toxicity level for the fish. Even though the nitrates are a lot less toxic than ammonia. If any of these are too high, the fish could die.

Newt: So what can I do to make sure my fish are healthy?

Becky: The most important part of tank hygiene is to maintain the nitrogen cycle with a cleaning cycle of your own. Ideally, you would start this process before you add any fish, but it is never too late to improve the lives of your little buddies. Add water conditioner and bacteria to the water to start this process. Let your tank water rest for at least a month while adding little bits of food to start your nitrogen cycle.

Newt: It's always safest to perform a water test before adding your fish. You'll want to check for the different parts of the nitrogen cycle of course, but you'll also want to check the pH level hardness and alkalinity. Once you have your water just right, only change out 20% of the things water at a time when cleaning.

Becky: Don't overfeed your fish either, as any uneaten food is going to add to the nitrogen cycle and throw things off balance.

Newt: This has been The Sound of Science on WNIJ, where you learn something new every day.