My Fish Tank Needs Cleaning

I completed this project as part of Professor Pringle’s EEB321 class at Princeton University. For this post, I decided to investigate what was growing on the inside surface of the glass of my fish tank. Here’s a picture of what it looks like from the outside:

Based on its coloration and some google searches, I thought that this might be brown algae. It’s interesting that it is growing in the condensation on the glass above the water level, and not within the water. According to this source, brown algae is a common occurrence in fish tanks and generally something that is not aesthetically pleasing, which I can attest to as seen above. I was wondering if it was having any negative effects on my fish tank ecosystem and while the source says that fish should generally not be harmed by it, it is generally not good for the home aquarium. To analyze it in more detail, I scraped some off of the glass and prepared a slide with it – this is what I saw through my foldscope.

It appeared an orange-brown color with small circular structures throughout. There were also regions that were lighter than others and some that were clearly darker than others, and I wondered why that was. Perhaps the darker areas are places of increased growth? I wasn’t sure because it looks pretty uniformly dark on the side of my tank, so I didn’t expect to see as much variation. Also, I wondered if the small circular structures were cells that had combined together to form the larger algal mass. In that case, the darker regions may be thicker than the lighter regions as there are more cells stacked on top of one another. I may need to brush up on my microscopy proficiency to answer these questions, but it was a fun task nonetheless!

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