Aquarium Care

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Aquarium Care Series: Aquarium Hazards

by Ruby Bayan,

Many years ago, I got involved in an aquarium decoration contest, where my winning entry was a tall 100-gallon tank that featured a fully set-up 5-gallon tank inside it. I can’t remember what fishes I put in there but I won the gold ribbon. I was proud of my ingenuity.

I often stretch my creativity when I decorate tanks for myself and others, but there are certain limitations and basic guidelines I work with, to ensure that my originality and ingenuity don’t become hazardous to the living creatures I have in my tank.


Water is the universal solvent, and anything that dissolves in water has the potential to pollute your tank environment. Therefore, the following water-soluble materials should never come in contact with the water in your aquarium:

  • Paper-based items
  • Textile or fabric
  • People food

In case of minor pollution accidents, and to minimize the hazardous effects of cloudy and contaminated water, consider adding water-conditioning products like EcoBio-Block, which uses beneficial bacteria to clarify and deodorize the habitat.

Toxic Materials

Chemicals dissolved in water can render your fishes ill in minutes. At high concentrations, toxic materials can kill them in seconds. Exposure to metallic substances that can contaminate the water, even in negligible quantities, can eventually stress the environment and make your pets susceptible to disease.

Here are some of the potentially toxic materials that you should keep away from your tank:

  • Metallic objects or toys, figurines, and knick-knacks that contain exposed metals
  • Dyed items that leach when wet
  • Oily items like crayons, modeling clay
  • Items that have come in contact with household chemicals like detergents, pesticides, cleaners, and solvent

Natural but Hazardous

Most often we are misled by the idea that since a decorative item is natural, it’s safe for the aquarium. Since we are maintaining freshwater aquaria, introducing driftwood, rocks, and shells that we picked up along the way can risk upsetting the “freshwater-ness” of the tank.

The rule of thumb is to refrain from introducing anything natural that may have come from a non-freshwater environment. The risk is that these items may be carrying mineral deposits, microorganisms, and parasites that existed in their natural locations.
Rocks, shells, and corals that may be innovative additions to your aquarium may leach calcium and other minerals that will affect the stability of your water composition. Driftwood can leach tannins that your fish may not be able to tolerate.

Many attractive artificial (hard plastic; inert) alternatives are available, and highly recommended, but if you would rather use natural wonders, here are tips to ensure they are safe to include in your setup:

  1. Wash the décor in clean running water, scrubbing off all loose particles. Do not use detergent. Boil rocks, shells, and corals for an hour or two for added measure. (Hint: Splash some vinegar on the rock/coral and if it sizzles, the item is calcium-rich and is better suited as a decorative accent on your bookshelf.)
  2. Soak the décor in a bucket of clean water for about a week or two and replace the water daily. This will help remove minerals and tannins that could leach in water.
  3. Dry the décor under the sun or in an oven to kill microorganisms and parasites that may still lurk within the item.

Moving and Disturbing

Those nifty action aquarium décor that opens and closes and goes up and down animated by bubbles rising from an air-stone can be quite engaging to onlookers. The pirate treasure chest, the little boy fishing, and the cute pearl clam — they look cute and interesting, but did you notice how they make some fishes nervous?
Eventually, the fish will get used to the animated items, but not before several days of stress and anxiety. By the time they get used to the jerky décor, it’s time to pull it out for a cleaning. Then when you put it back in, the fish will become jittery again. So, use your better judgment when using these supposedly attractive decorations.

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