Cloudy aquarium water tends to limit the visibility inside the tank. Turbidities may appear in the form of milky-gray water, or as suspended particles visible to the naked eye, or as a greenish stain in the water. Depending on the color, the turbidity in the aquarium is caused by different phenomena. In the following describe some typical causes for cloudy water in the aquarium, as well as solutions on how to fix them.

Visible suspended particles

Floating particles, visible to the naked eye, can be removed pretty easily: Simply use a flocculant such as Seachem Clarity or Microbe-Lift Clarifier Plus Freshwater. These products bind to the suspended particles which then sink to the bottom or get sucked in by the filter. If, due to strong flocculation, bigger clusters accumulate on the substrate, they can be hosed off easily with an aquarium hose. Usually the majority of the dirt particles is caught by the filter, and therefore it is a good idea to clean the filter material some time after applying the flocculant.

Turbidities caused by suspended particles are often the consequence if the muck at the bottom of the tank is disturbed, or by fine substrate particles, e. g. through the activities of burrowing fish or if you redecorate your tank. If this kind of turbidity is a permanent problem, you might want to re-consider which filter media you use in your filter. Fine-pored materials such as fine filter fleece will help you remove the particles mechanically from of the water. These media should be cleaned and/or changed regularly to prevent the filter from clogging. The especially fine Symec Micro filter fleece by JBL has proven to be especially effective. It only needs a very short time to remove even the tiniest suspended matter from the water - but it also slows down the water flow of the filter. So we recommend this product rather as a short-term means to get rid of turbidities than for continuous operation. When the aquarium is newly set-up, many fine particles from the substrate and decoration get swirled up. These can be easily removed within only a day if you use JBL Symec Micro.

Milky or green water

Milky or green stains in the water indicate an algal or bacterial bloom. This phenomenon can pop up quite suddenly and be caused by e. g. seasonal fluctuations. For a more detailed description we recommend reading the articles "Bacterial bloom" and "Green water". In both cases, the short-term use of a UVC clarifier is recommended.

Brownish water

This phenomenon is less of a turbidity and more of a water discoloration. The water assumes a yellow to brown stain which is often caused by humic acids, which are often released by fresh driftwood or soil. For this reason, a brown stain often occurs during the start-up phase in aquariums with driftwood. Filter media such as Seachem Purigen clean up the water in no time. As an alternative, you can remove the stain with several generous water changes. You don't have to, though, since humins are usually not harmful to the aquarium inhabitants, at least not in the amount emitted by driftwood.