4 Annoying Pests Found in Your Freshwater Aquarium

Summer Davis
by Summer Davis
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.

To get rid of algae, try this: Tetra AlgaeControl Water Treatment

This liquid formula has a broad spectrum of effectiveness and it will successfully work on all kinds of algae, including green water (algae blooms), blue green algae, brown algae, and hair algae or blanketweed. This water treatment is completely safe for the fish and the plants in the aquarium, but as all algaecides, it is not safe for snails or other invertebrates. One drop of this solution cleans a gallon of water, so a little goes a long way- with one bottle, you can treat 1,200 gallons. For best results, combine this product with manual removal of algae with scrapers and/or cleaning magnets.

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.

If you want to kill planaria without harming your flora and fauna, try this: SL Aqua Z-1

No one wants yucky worms in their gorgeous fish tank and the fastest way to eliminate them is to eradicate them with a chemical. Luckily, this product uses natural extracts to kill planaria and hydra both but it’s completely non-toxic to shrimp, fish and plant life in your aquarium! The 10 gram pack can treat 132 gallons of water- and each treatment cycle lasts a week. Depending on the severity of the infestation, you might want to repeat the treatment. Important to note- this product will also kill all types of snails, so it’s not recommended for tanks that house these well-loved crustaceans.

To keep the grave clean and free of planaria, try this: VIVOSUN Aquarium Gravel Cleaner Siphon

Regular cleaning and proper maintenance can help a lot with pest problems, but especially with planaria. Use the net from the set to scoop up the worms that are slinking around and the handy syphon cleaner to suck out these nasties from your gravel.

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.

For a product that eradicates hydra and planaria both, try this: Benibachi Planaria Zero

Like having issues with one type of pest isn’t enough, infestations with planaria and hydra often go hand in hand. And even when you “just” have hydra in your aquarium, this powerful solution will help you get rid of it in no time: made from natural palm family betel wax powder, it will completely eradicate both hydra and planaria. Unfortunately, it also kills snails- so if you have pet snails in the tank, this one is a no-no.


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.

In case you want to completely eradicate snails from your fish tank, try this: Seachem Cupramine Copper

Not all snails are welcome guests in the aquarium, and if you are so fed up with them that you want to eliminate them completely, then this copper solution will do the trick. Just use with care as copper can harm many other aquarium dwellers and plants.

Alternatively, if you prefer humane methods and don’t want to kill the snails just get them out of your tank- try this: ISTA Snail Trap

If your veggie baits aren’t working as well, this specially designed trap for aquarium snails is the option for you. In addition to the trap, you’ll also get snail bait- everything you could possibly need to successfully and humanely treat the snail problem in your fish tank.

We are committed to finding, researching, and recommending the best products. We earn commissions from purchases you make using the retail links in our product reviews. Learn more about how this works.

Summer Davis
Summer Davis

Summer 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."

More by Summer Davis