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10 Common Freshwater Aquarium Problems and How to Solve Them

10 Common Freshwater Aquarium Problems and How to Solve Them

#1: Cloudy aquarium water

After starting a new freshwater aquarium it’s common to have a little cloudy water during the first week. After the fish are added and you begin feeding, a slight haziness will often appear. This is caused by a harmless bacteria bloom. Aquariums rely on microscopic bacteria to clean up fish waste. The beneficial bacteria enter the aquarium on the surface of the fish. They live in the water and in the aquarium gravel. In a new aquarium you’ll often see an initial burst of bacterial growth as they settle in and start cleaning up fish waste. This will cause a slight cloudiness in the water. This is natural and will clear up in about a week. Don’t panic and drain the aquarium! If you over-feed, the bacteria will feast on the excess fish food and fish waste, causing a permanent cloudy water problem. There should never be uneaten food floating at the water surface or on the gravel. If there is, reduce feeding and siphon out uneaten fish food. Most new aquarists over-feed their fish. This causes water quality problems that result in sick fish. Aquarium fish are perfectly happy with one or two small feedings per day. Your fish will always act like they’re hungry, but resist the urge to feed too much.

#2: Aquarium odor 

A healthy freshwater aquarium never smells bad. If it does, you’re probably over-feeding. Fish food and fish waste collect in the gravel bed, creating a dark sludge layer. If the aquarium gravel is dirty, use a gravel siphon once a month to keep it free of sludge. An occasional earthy odor is natural. It’s caused by substances released by algae. Activated carbon filtration will remove these odors and give the aquarium a fresh smell. Old filter media clogged with debris will cause odors and lower the water quality. Clean the aquarium filter and use fresh filter media at least once a month. 


#3: Fuzzy white patches

If you see white fuzz growing in your aquarium gravel, you’re adding too much fish food. Uneaten fish food soaks up water and falls to the bottom of the aquarium. Natural fungus will quickly start feeding on the food particles. The fungal colony looks like fuzzy growth on the gravel or anywhere food particles are resting. Use a gravel siphon to remove the fuzzy particles. If you find fuzzy particles in your filter, change the filter media right away. Cut back on the amount of food you’re giving the fish. It is more than they can eat. 


#4: Algae on the glass and gravel

Algae are tiny aquatic plants that grow in water. Every aquarium, no matter how clean, contains millions of algae cells in the water and on the surface of the gravel. Algae are a part of the aquarium’s ecosystem. Normally, algae remain unseen. Occasionally you’ll have to clean the aquarium glass and decorations. Since algae are plants, they thrive when there are plenty of nutrients in the aquarium water. These nutrients come from fish food, fish waste and tap water. Monthly water changes help to dilute nutrients and inhibit algae growth. Change 20-30% of the water every month. If you see algae start to grow on the glass, scrape it off right away. It’s easier to clean a small patch than to wait until the entire tank is covered with algae.

#5: Green water

Green aquarium water is caused when free-floating algae grow so fast, they discolor the tank’s water. Even when aquarium water looks clear, there are millions of free-floating algae cells swirling around. A natural balance among many types of algae exists in most tanks. If the nutrients get too high or if there is excess light, it can trigger an algae bloom. One species tends to take over, causing the water to look like pea soup! Sometimes the algae imbalance corrects itself. Turning off the aquarium light for a week may trigger an “algae reset” and clear the water. Reduce lighting to no more than 10 hours a day. Make several partial water changes (20%) over a week to dilute nutrients. In some cases, temporary use of an algaecide is the only way to control the algae and restore a natural balance.

#6: Mineral build-up on the aquarium

Does your aquarium have a white, crusty mess around the top of the tank? This is caused by mineral build-up. As the aquarium water evaporates it leaves behind calcium and other minerals. Aquarium filter and aeration devices create a lot of splashing and mist at the surface of the water. Some of this water can coat the top of the aquarium, the light and the lid. As the water dries, it leaves behind a hard crust. The longer it builds up, the harder it is to remove. Keep the water level in the aquarium high to reduce splashing. Turn down bubbling ornaments or reposition them so the rising bubbles don’t cause wetness at the back of the aquarium. Wipe away minerals once a week. If the crust is hard to remove, wet it with white vinegar. Vinegar is a mild acid that dissolves minerals. If your light and glass cover is crusty, take it to the sink for cleaning. Wipe it down with vinegar. The crust will bubble as the vinegar dissolves and loosens the minerals. A toothbrush will help with the clean-up. Rinse off excess vinegar and minerals with water when you’re finished.

#7: Snails

Some aquarists like to keep a snail or two in their tank. Some species are large and are interesting to watch as they glide around the aquarium. But certain snail species can become a problem. They reproduce so quickly the entire aquarium can be a mass of snails. These small varieties often work their way into the filter intake, jamming up the motor. Aquarists often wonder how the snails got into the aquarium. There are several ways. Snails and snail eggs often sneak in on live aquarium plants. Before adding them to the tank, inspect the plants for snails or jelly-like egg masses. The Malayan trumpet snail is a live-bearer. You won’t find any eggs, but the snails produce lots of live baby snails. Don’t make the mistake of allowing a few of these pest snails to remain in your tank. Before you know it there could be hundreds of snails in your aquarium. You can use a special snail trap to capture them. Avoid chemical snail treatments, as they contain copper which is ineffective and can even hurt your fish in large doses. One natural way to keep snails under control is with a loach. Loaches are interesting tropical fish that find small snails very tasty. A loach or two will gradually eliminate the small, pest-type snails in your aquarium.


#8: Discolored water

Discolored water is different than green water and cloudy water. Over time aquariums accumulate organic pollutants that give the water a yellowish tint. These organics change the way your tank looks. The color of fish, plants and decorations won’t be as vibrant because the organics absorb some of the light. Discolored water is common in tanks containing a lot of fish or fish that are fed heavily. But even a well-cared for aquarium will develop a yellow tint over time. Monthly water changes help remove the organics. Using fresh activated carbon or changing the filter cartridge will also help keep the water crystal clear!

#9: Sick fish

This is a complicated topic with no simple answers, and is a subject for another in-depth article. There are a variety of reasons why aquarium fish get sick. The most important thing you can do to keep your fish healthy is to take care of the water quality. Test the ammonia and nitrite levels frequently. There should never be any detectable ammonia or nitrite in the water. Low levels stress the fish and weaken their immune system. This makes it easier for them to get sick. Check the water temperature. Tropical fish need warm water to stay healthy and active. Tropical fish prefer warmer water in the 72-82˚F/22-28°C range. Use an aquarium heater to maintain a steady water temperature.

#10: pH level

Many aquarists worry that the pH in their tank is not at a specific level. Many stress out, for example, if the pH is 7.2 instead of 7.0. The truth is if your freshwater aquarium has a pH of 6.8 to 8.0 there is no need to change it. There is no need to worry about fine-tuning the pH to reach a specific level. As long as the pH does not shift below or above the recommended range, all will be well! It is important to test the pH monthly because pH can creep to unsafe levels. Periodic water changes often bring the pH back in line. If not, use pH-adjusting products made for aquarium use.

comments ( 1 )

Bob Morris REPLY
Jan 02, 2022

Very helpful! Thanks for this.

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