Why Fish Tanks Get Dirty Fast and How to Prevent It

Keeping an aquarium is a great way to add beauty and interest to your home and a popular source of relaxation, education, and entertainment. Like most hobbies, there is no limit to the options you can choose to personalize your aquariums. Whether you keep it simple or enjoy the challenge of tackling complicated projects, you’ll need to keep the aquarium clean.

Why fish tanks get dirty fast and how to prevent it. Depending on the species you keep, the size of the tank, and your cleaning and maintenance routines—there are many potential reasons that an aquarium can get dirty quickly. Fortunately, there are pretty straightforward solutions for almost every problem.

Some species are just dirtier than others, while other species can actually pitch and help keep a tank clean. Getting the right mix, giving everyone enough space, identifying the right size and type of filter, and getting into a regular maintenance routine will help keep your aquarium clean. Read on to learn more about our top tips and tricks for preventing a dirty tank.

Why the Tank Gets Dirty Fast

Every aquarium is a self-contained biosphere. If your aquarium achieves the right balance, it will be almost self-sustaining. The more your tank’s environment diverges from this balance, the more work that you’ll have to do to keep it clean. A clean tank is not only more fun to watch but also important for the health and happiness of the residents.

The first step in setting yourself up with an aquarium that stays cleaner longer is making sure that your tank has enough volume for the number of fish and particular species that you’re keeping. If your tank is overstocked, it will definitely get dirty faster and require more work at more frequent intervals.

Another important element in your aquarium set-up is the filtration system. Making sure that it is the right size and has enough power to cycle the tank’s volume at an appropriate rate is crucial to keeping your tank clean between regular maintenance. It’s equally important to make sure that you follow the appropriate steps in cleaning and maintaining the filter.

Once you have your basic set-up right-sized for the fish that you want to keep, there are tips and tricks that you can use to tweak your aquarium’s environment in order to get it clean and keep it that way. These range from daily feeding practices to weekly and monthly maintenance schedules. When you find the right mix, you should be able to relax and enjoy your aquarium.

How to Prevent It

Paying close attention to “how” your tank gets dirty will point you in the right direction with regard to searching for solutions. Cloudy water or suspended solids indicate problems with the aquarium’s filtration system. Algae growth signals an imbalance in nutrients that can be due to overfeeding, too much light, or overstocking.

When it comes to preventing a dirty tank, it’s better to overdo it on the filtration system. Make sure the filter is not only the right size to handle the volume of your tank but also capable of moving the gallons per hour filtration rate that is appropriate for the species in your tank. Treat the beneficial bacteria in your filter element with the same care that you treat your fish.

Overfeeding your fish is one sure way to end up with a dirty tank. The food that gets eaten by your fish ends up as waste that your filtration system can deal with. Uneaten food ends up as suspended solids in the water and leads to a nutrient-rich environment that promotes algae growth. Too much light can plus too many nutrients can put algae in overdrive.

The things that you do on a daily, weekly, and monthly basis will go a long way toward preventing a dirty tank. You will need to develop a routine that works for the tank you have and the species that you keep.

  1. Daily Tasks
    1. Check on your tank every day.
    1. Feed the right quantity and make sure it is consumed completely and immediately.
    1. Do a quick inspection of the filter, lights, and heater to ensure that they’re working properly.
    1. Observe your fish for any signs of distress or disease in the appearance of their skin and the way that they’re swimming.
    1. Take note of the water to verify that there are no foul odors, floating solids, or other issues.
  2. Weekly Tasks
    1. If you keep live plants in your aquarium, you will need to remove dead leaves and perform routine trimming on a weekly basis.
    1. Remove algae from the sides of the tank using a scraper or magnet.
    1. Replace 10-20% of the tank’s volume with fresh dechlorinated water.
    1. Wipe the aquarium’s glass with a clean rag—never use chemicals or soap to clean the aquarium glass!
  3. Monthly Tasks
    1. Vacuum aquarium gravel to eliminate solid waste.
    1. Perform a higher-volume water replacement if conditions warrant it.
    1. Perform a thorough inspection of the filtration system, heating elements, and other equipment to ensure that everything is in good shape.

Tips and Tricks for Keeping Your Aquarium Cleaner for Longer

So far, our discussion has focused on the elements that are important to laying a solid foundation for your aquarium. Getting enough tank and filter for the plans you have and getting into a regular routine are the most important first steps to long-term success in keeping a clean and enjoyable aquarium without having to perform constant maintenance.

Once you’ve laid your foundation, there are a number of areas where you can make adjustments to fine-tune the results that you’re getting until you’re satisfied with the level of effort your tank requires and the state that it’s in between cleanings.

Any time you’re setting up a new tank or making major changes to the routine for one that has been up and running for a while—be patient. It can take time for things to return to stable after you make a change. It’s best to make “tweaks” one-at-a-time and to allow the tank to re-stabilize between each tweak.

Tip #1 – Bio-Load

Every one of the animals in your aquarium produces waste, which is then broken down by microorganisms. In the process of breaking down waste, these microorganisms consume oxygen, and the broken-down waste winds up as ammonia and nitrites.

Your fish, shrimp, snails, and other residents need the oxygen in your tank’s water. So, the process of breaking down waste is using a resource that they need and producing a byproduct that is toxic to them. Your filtration system changes the ammonia and nitrite into the less toxic nitrate. Regular water changes reduce nitrates and restore oxygen levels.

This is, in very broad strokes, the cycle of life for the inhabitants of your tank. Anything that increases the bio-load is going to increase the number of algae and free-floating bacteria in your tank. Overstocking and overfeeding are the easiest contributors to high bio-load for aquarium keepers to control.

Performing regular water changes is essential to maintaining a low bio-load. Performing filter maintenance as needed to prevent clogging is also important.

Tip #2 – Filtration

Newcomers to aquarium keeping will often shop for filters based on whether they are rated for the size tank they’re going to keep. If you’re going to keep an aquarium that maintains a sparse population, practices sparse feeding, and keeps to a regular routine of water changes—this type of rating will be fine to use when selecting a filter.

A more accurate and reliable way to assess your filter’s capabilities is by looking at it’s flow-rate, which is measured in gallons per hour (GPH). Even then, the GPH rating will only tell you what the filter pump is capable of. The lines and hoses your use, filter elements, and other parts of the system will introduce resistance that will reduce the actual flow-rate.

If you want to know exactly what your tank’s set-up is capable of supporting, you’ll need to do a flow-test and calculate your tank’s precise turnover rate.

Follow these steps to find out your tank’s turnover rate:

  1. Conduct a Flow-Test to Get the GPH Flow-Rate
    1. Prepare a sterile container that holds a gallon or provides graduated measurements.
    1. Turn off your pump and run a length of plastic tubing from the pump’s outflow nozzle to your container.
    1. Using a stopwatch to measure the time it takes, turn on the pump and let it run until you have a gallon of water in your container.
    1. Make a note of the time that it took. Return the water to your tank and return your filter to service.
    1. Divide the time that you recorded on your stopwatch by 60 to get your gallon per minute rate.
    1. Multiply the gallon per minute rate by 60 to get the gallon per hour rate.
  2. Calculate the Tank’s Turnover Rate
    1. Determine the height, width, and depth of the tank area that holds water—do not include the area of the tank that is filled with the substrate or the area at the top of the tank that does not contain water.
    1. You can do the math yourself or use an online tank water volume calculator to do it for you, but you need to convert your measurements into a precise measurement of the water in your tank in gallons.
    1. Divide your GPH flow rate by the volume of water in your tank to get the turnover rate.

Knowing the turnover rate will help you troubleshoot any issues that you’re having if you continue to have problems keeping your tank clean. Some species require a higher turnover rate than others. If you think you have enough tank and filter for the number of fish but still have a dirty tank, you may need to increase your turnover rate.

Tip #3 – Overfeeding

Overfeeding is a common problem. The right amount to feed your fish will probably seem like too little, and you’ll worry that you’re starving them. But overfeeding has a significant impact on water quality, algae growth, and filter performance and lifespan. If you want a clean and happy aquarium that you don’t have to work on constantly, it’s worth it to conduct a feeding test.

To conduct a feeding test:

  1. Feed your fish the amount that you normally do.
  2. Time how long it takes for the fish to consume all of the food.
  3. Remove any leftover food with a skimmer net or siphon.
  4. Over time, gradually reduce the amount that you are feeding your fish until
    1. All of the food is consumed
    1. It is all consumed within 4-5 minutes

Be sure that everyone in your family and anyone who does house-sitting or pet-sitting for you know the right amounts of food and the schedule for your aquarium feeding routine. It’s important that everyone stick to the routine if you’re going to eliminate problems in your aquarium that are caused by leftover food.

One way to tackle the problems caused by overfeeding and leftover food is to invest in an automatic fish feeder. They can be a great way to keep everything on a routine, whether you are going to be home every day or traveling for a time.

Tip #4 – Light

If you have problems with algae in your tank, then you definitely have too many nutrients in your water. Eliminating overfeeding and making sure that you have the right filter for your tank are important first-steps in eliminating this problem. But another piece of the puzzle that deserves some attention is the amount of light that your tank receives.

A tank that’s water is holding too many nutrients will support algae. When a tank like that is exposed to light, the algae can go into overdrive. When you’re having problems with algae in your tank, you should limit the tank to 6-8 hours of light per day to help you control the problem.

If your tank is near a natural light source like a window, you might need to invest in blackout curtains to help you limit the amount of light that your tank receives each day. If your tank is in an area that doesn’t receive direct light from a natural source, you will just need to be vigilant about making sure you turn the tank’s light off and on at the appropriate times.

Tip #5 – Species

As we discussed earlier, some species of fish are just dirtier than others. The common goldfish is notorious for its ability to contribute to a high bio-load in any tank. At the same time, there are some species that will definitely lend a hand when it comes to keeping things around the tank tidied up.

A note of caution before we go into a discussion of the particular species that get good marks for cleaning up an aquarium. Remember that every animal that you add to your tank will contribute to the overall bio-load of the tank. So, you can’t “fix” a dirty tank just by adding a few fish or snails that will eat algae.

With that being said, when you’ve gotten your tank into a stabilized routine and gotten a handle on a manageable bio-load—these species will help you out by feeding on algae or otherwise tidying up after their roommates.

  • Nerites Albicella – These snails are hearty and will do a lot of work to keep the algae in your tank under control. Just make sure to keep a cap on your aquarium, or they’ll escape.
  • Bristle Nose Pleco – An interesting and attractive fish that won’t disrupt the tank’s environment or bother your other fish.
  • Corydoras – One of the most popular options for a clean-up catfish.
  • Mollies – Popular with beginners and available in a wide variety of colors.

Wrapping Things Up

Keeping an aquarium should be a fun and relaxing hobby. It is an easy enough activity to get involved in and offers limitless possibilities for those who want to branch out from their initial set-up to take on more challenging and more diverse arrangements. But for beginners and advanced aquarium keepers alike, part of enjoying the hobby is minimizing the amount of work.

It’s hard to enjoy an aquarium that looks dirty and disgusting. It’s just as hard to enjoy an aquarium when you have to spend all of your free time keeping it clean and looking good. Laying the right foundation for your tank will go a long way toward making maintenance a manageable routine.

Following the tips and tricks that we’ve provided in this article ought to give you plenty of ideas for fine-tuning your maintenance routine into one that works for you and your fish. Remember to be patient and introduce changes one-at-a-time. Allow the tank to stabilize before making more adjustments or introducing anything else new. That way you won’t end up going in circles.

Good Luck!

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Adam Edwards
Hi, my name is Adam and I'm an aquarium enthusiast! I didn't discover the joys of being an 'aquarium fanatic' (as some of my friends call me!) until I was in my 20's. When I first started out I found it difficult to find all the information I needed so I started this website to compile all the useful information I can think of. Enjoy!