Why is My Cat Fountain Slimy & Gross? Get to the Bottom of the Gunk


Cat water fountains have become a popular way to encourage cats to drink more water. The flowing water attracts feline interest, and the filtration system helps keep the water clean. However, plastic cat fountains are prone to developing a slimy biofilm over time. This buildup occurs due to scratches in the plastic that form breeding grounds for bacteria and algae. While harmless to pets, the slimy layer in cat fountains can look unappealing to owners. With proper maintenance and cleaning, slimy buildup can be minimized or prevented. This article provides an overview of why slime develops in cat fountains and how to manage it.

Benefits of Cat Water Fountains

Cat water fountains provide numerous benefits for cats’ health and happiness. The constant circulation and filtration system keeps the water fresh and appealing, which encourages cats to drink more. Increased water consumption helps cats stay hydrated, prevents urinary tract infections, and reduces the formation of bladder crystals and stones (Source).

The ever-flowing stream mimics natural drinking sources, which entices finicky felines to drink. Cats tend to avoid drinking stagnant water, so a fountain provides a healthy drinking alternative. The increased water intake helps dilute toxins and aids kidney and liver function. Proper hydration also enhances nutrient absorption from food and may prevent conditions like constipation, kidney disease, and urinary blockages.

Causes of Slimy Buildup

Slimy buildup in cat water fountains is primarily caused by three things – biofilm, algae, and hard water minerals.

Biofilm refers to a thin layer of bacteria that accumulates on any wet surface over time. As water flows over the fountain, bacteria stick and multiply on the interior surfaces and tubes. This biofilm can become slimy in texture as more moisture and nutrients allow the bacteria to thrive and reproduce rapidly 1. Plastic fountains are especially prone to biofilm growth due to the tiny scratches in the plastic that bacteria can attach to 2.

Exposure to sunlight can also cause green or brown algae to accumulate in cat fountains, contributing to the slimy film. The warm, moist environment coupled with nutrients from the water, plastic, and cat saliva create ideal conditions for algae.

Finally, hard water containing dissolved minerals like calcium and magnesium carbonate leaves mineral deposits over time. These minerals can leave a whitish slimy coating or clog small parts of the fountain.

Preventing Slimy Buildup

There are a few key things you can do to help prevent slimy buildup in your cat’s water fountain:

  • Clean the fountain regularly according to the manufacturer’s instructions. Take apart all components and wash thoroughly with hot water. You may need a bottle brush to scrub inside crevices. After cleaning, rinse everything thoroughly.

  • Use filtered water rather than tap water. Tap water contains minerals and contaminants that can contribute to slimy buildup over time. Filtered water will help minimize this.

  • Add antibiotics to the water occasionally. According to this Reddit thread, adding a capful of 3% hydrogen peroxide to the water every few days can help prevent slime. The hydrogen peroxide breaks down into water and oxygen over time.

Keeping the fountain clean, using filtered water, and adding hydrogen peroxide can all help prevent the growth of slimy biofilm over time. Be sure to inspect the fountain regularly and clean whenever you notice any cloudiness or slimy buildup starting.

Cleaning Methods

Cleaning the fountain regularly is crucial to preventing excessive slimy buildup. There are several effective cleaning solutions to remove the biofilm.

The most common homemade cleaner is vinegar. Mix equal parts white vinegar and warm water and soak all the fountain components for 30 minutes to an hour. Vinegar is an acidic cleaner that breaks down mineral deposits and dissolves organic buildup like biofilm. Rinse thoroughly after soaking.

Another good option is hydrogen peroxide, diluted to around 3% concentration. Hydrogen peroxide is an oxidizing agent that bubbles away grime. Let the fountain parts soak for 20-30 minutes. Be sure to rinse off any residue afterwards.

Lemon juice is a natural acidic cleaner like vinegar. Squeeze fresh lemon juice into warm water and soak the fountain. The citric acid will help dissolve the slimy film. Rinse thoroughly and air dry pieces before reassembling.

For tough slimy buildup, combine vinegar and lemon juice for an extra cleaning boost. Soak for an hour, scrub with a soft brush, then rinse.

Commercial Cleaning Products

There are several commercial cleaning products designed specifically for cat water fountains that can help remove slimy buildup and prevent it from recurring. Some popular products include:

PetSafe Drinkwell Fountain Cleaning Kit – This 3-brush kit is designed for Drinkwell fountains and includes a big brush with a soft sponge to scrub away slimy buildup. According to reviews, it’s effective at removing tough stains and leaving fountains fresh.

Tetra Waterfall Globe Cleaning Kit – Specifically made for Tetra waterfalls and globes, this kit contains a long brush, cleaning pad, and bio-cleaner to break down slime and prevent its recurrence. The biodegradable formula is safe if cats ingest it.

Aquasana Cat Water Fountain Cleaning Kit – Contains small brushes, long bristled brushes and a stone cleaner ideal for scrubbing nooks and crannies. Works well on their plastic and ceramic fountains. Aquasana also sells descaling solution.

You can find these commercial cleaning kits at major pet stores, online retailers like Amazon and Chewy, and directly from the fountain manufacturers’ websites. Prices range from $5-15 depending on the brand and components included.

When to Replace

Over time, cat water fountains can start to break down and function less optimally. Signs that it may be time to replace your cat fountain include:

  • The motor is making loud noises or vibrating excessively[1]
  • Water flow has slowed down or stops completely
  • Parts are cracked, chipped or broken
  • The fountain has a strong odor that can’t be eliminated by cleaning
  • It’s difficult to fully disassemble the fountain for cleaning
  • Filters need replacement more than once a month[2]
  • Your cat has started avoiding the fountain

If you notice any of these issues, it’s probably time to purchase a new cat fountain. A good quality fountain should last 1-2 years with proper maintenance. Investing in a replacement can help ensure your cat continues to drink adequate amounts of clean, filtered water.

Choosing a New Fountain

When it’s time to replace an old, slimy cat fountain, there are a few key features to look for in a new model:

Materials – Ceramic and stainless steel fountains are more hygienic and easier to clean than plastic models. Ceramic tends to be more attractive but also more delicate.

Size – Consider how many cats will be using the fountain and opt for a larger size if needed. Larger reservoirs require less frequent refilling.

Filters – Multi-stage filtration systems help keep water fresh and prevent buildup. Activated carbon filters are excellent at removing impurities.

Flow control – Adjustable water flow allows customization for your cat’s preferences. Lower flow reduces splashing.

Easy cleaning – Disassembleable parts that are dishwasher safe make cleaning fountains much simpler.

Some top-rated cat water fountain models include:

Pioneer Pet Raindrop Stainless Steel Drinking Fountain – durable stainless steel basin, activated carbon filter, low-voltage submersible pump.

Petsafe Drinkwell Pagoda Ceramic Fountain – ceramic construction, dual free-falling streams, replaceable carbon filter.

PetKit Eversweet II 3L Automatic Cat Water Fountain – BPA-free plastic, triple filtration system, quiet submersible pump.

Veken Pet Fountain – affordable plastic model with two water streams, replaceable filter, and low noise level.[1]

Alternatives to Fountains

While cat water fountains can have benefits like encouraging hydration, there are alternatives cat owners can consider besides fountains. Some options include:


Using a regular water bowl is a simple alternative to a fountain. Bowls are inexpensive and easy to clean. However, some cats may not drink enough water from a regular bowl. Moving water can be more enticing for cats to drink.

Faucets and Sinks

Some cats prefer to drink fresh running water from faucets or sinks. This provides the appeal of moving water. Allowing cats access to sinks comes with some downsides though. It can lead to more accidents and messes if cats start playing in or around the sink.[1] Using a sink as the primary water source is not as sanitary as other options.

Self-Refilling Bowls

Self-refilling or self-replenishing bowls provide fresh water without the moving water appeal of fountains. The bowl automatically refills itself as the cat drinks. This gives fresh water but without the fountain pump and filtration. It’s an alternative to consider for cats that just want fresher water in a simple bowl.

While fountains have advantages, alternatives like bowls can also work well for many cats. The options can be weighed based on cats’ preferences, convenience, and maintenance considerations.

[1] https://cats.com/best-cat-water-fountain


A cat water fountain can encourage your feline friend to drink more water, which contributes to good health and long life. However, the moist environment that makes it so enticing to cats can also promote slimy buildup from bacteria, minerals, and algae. With proper maintenance like daily and weekly cleaning, slimy buildup can be kept under control. Substrates like plastic and ceramic may be less susceptible than stone or metal. Watch for excessive buildup and discoloration as signs to scrub or disinfect the fountain. Consider using cleaners made specifically for pet fountains to simplify the process. In extreme cases, replacing the fountain entirely may be necessary. Providing your cat with a clean water source is crucial for hydration and reducing the risks of urinary or kidney problems down the road. With the right fountain and regular cleaning, you can keep the water fresh and appealing for your feline friend.

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