March 23, 2023

4 Annoying Pests Found in Your Freshwater Aquarium

Even the smallest pests can mess up the most pristine aquarium. Here are four common (and annoying) pests that could cause problems in your freshwater tank.

Your aquarium is at risk of many types of pests, but do you know what to look for? From single-celled organisms to cagey creatures, you should be aware of the pests that can wreak havoc on your tank.


This one is pretty common, and is identifiable by most people. It is a single-celled organism that thrives in the same way that plants do – from light. Some algaes that can grow in your tank include black beard algae, blue green algae, clado, diatoms, and thread algae. Treatment of this issue is pretty straightforward – limit light and nutrients, or use an algecide to treat your tank. Without treatment, algae are not only unsightly, but also can choke out any live plants you may have.

Related: Growing and Controlling Algae in Your Aquarium


Planaria are flatworms that can live in both fresh and saltwater. They are more common in fresh water tanks, however. These white or pinkish worms can sometimes been seen slinking around on the glass. To prevent planaria, be careful not to overfeed the tank. If planaria are sighted, do not try to squish or cut them, as they can regenerate into multiple planaria. You must either remove them from the tank with a net or syphon, or use a chemical to kill them. The good news is that aside from being a little gross, planaria are not harmful to fish, and some fish may even eat them. If you notice them in your tank, don’t panic. Just keep calm, vacuum the gravel and cut back on feeding.

Related: Top 5 Invertebrates to Hire For Your Freshwater Cleanup Crew


Hydra are freshwater polyps, around an inch long. They have one sticky “foot” on one end that they use to keep themselves stationary, and a dozen tentacles on the other end. These tentacles have the ability to sting their prey and immobilize them, and this includes small fish or fry.  They reproduce quickly, and can cause a lot of damage in an aquarium. Hydra are similar to jellyfish in that they have no brain or repertory system. Eliminating these from a tank can be difficult, but can be done by soaking plants in a 10 percent bleach mixture for about 10 minutes and a thorough scrubbing. Some fish, such as three-spot gouramis or mollys, will eat these dangerous pests. Pond snails will also help get rid of them.


This last one is pretty subjective, as some people love snails while others loathe them. There are many snails that can live in aquariums; some are more wanted than others. Varieties like pond snails and ramshorn snails are sometimes viewed as a nuisance, mostly because of how quickly they can multiply. They are not harmful to the fish, and do help cut back on waste. To eliminate some of the snails in a tank, just toss in some vegetables and wait; they will congregate on the veggie and can be removed en masse. If getting them out entirely is the plan, a copper solution will do the job, however be warned that it will stick around in the tank for a long time, and will harm or kill any inverts that are ever in the tanks.

summerSummer Davis is the mom of three kids, four dogs, and several tanks of fish. She boasts a passion for all animals, whether they are in the water or on land. This fish aficionado has kept many different species in her time, but holds a special place in her heart for wild and domestic bettas. When she’s not talking about fish, Summer “spins” her extra time as the director of a baton twirling organization.