Peat Moss for Fish

Written by tom wagner
  • Share
  • Tweet
  • Share
  • Pin
  • Email
Peat Moss for Fish
Adding peat moss to your aquarium or fishpond can benefit certain species of fish (fish pond image by Pawel Dowgiallo from

Tap water varies widely depending on where you live. Municipal water sources often add minerals to water to make it safer to drink; filtered water extracted from streams and rivers may have a naturally high concentration of minerals. These minerals make water alkaline, or “hard”, and while many species of fish thrive in hard water, several tropical varieties prefer soft or mineral-deficient water. Adding peat moss to aquarium or fishpond water is an excellent way to remove some of these minerals.

Soften Water

Peat moss contains humic acid as well as tannic acid. Humic acid is a product of humus, partially or fully decayed organic vegetable or animal matter used by plants as a nutrient. When you add peat to hard water (water with high levels of minerals), the negatively charged humic acid molecules bind with both positively charged magnesium and calcium ions, removing these minerals from the water and thereby softening it.

Lower pH

A neutral pH level is 7.0; anything higher than this is alkaline and anything lower is acidic, and the greater the deviation from a pH of 7.0, the more acidic or alkaline the substance. Peat moss contains both humic and tannic acids; when the molecules of humic acid bond with magnesium and calcium, the minerals release free positively charge hydrogen into the water, lowering the pH and thereby making the water acidic.

Encourage Spawning

Most species of fish spawn, or lay eggs, during their regional rainy season, when rivers and streams swell. Rain releases tannic and humic acid contained in peat-rich soil, which then flows into waterways. Many types of fish can detect this and will correlate the addition of peat moss into an aquarium or pond as a signal to spawn.

Varieties of Peat Moss

Gardening, home improvement and some pet stores sell several selections of peat moss from which to choose. Those sold in pet stores specifically for aquariums are often in disc or pellet form and are rather expensive. You need not spend a lot of money on peat moss. As long as it doesn’t contain additives such as fertilisers, you can buy it for little money at gardening supply stores.

How to Use Peat Moss

You can simply drop peat moss pellets or discs sold in pet stores into your aquarium or pond without preparation. For gardening peat moss, place it into a bucket, pour boiling water over it and let it steep overnight. This will keep it from floating and staining the water too much when added to the aquarium or fishpond. Drain the moss and wrap it while damp in some type of tight-mesh fabric, seal it and place it into your filter. It will colour the water slightly, but this accentuates the colours of fish. Use a litmus pH test-kit to check the acidity of your water periodically; when the pH begins to rise, replace the peat moss.

Fish that Thrive in Acidic Water

Some fish, such as plecostomus fish, prefer mineral-rich hard water with a higher pH. Before adding peat moss to your aquarium or fishpond, make sure that the fish you have prefer low-pH soft water to hard water. Some species of fish that favour soft water include angelfish, dwarf gouramis, neon tetras and cory catfish.

Don't Miss

  • All types
  • Articles
  • Slideshows
  • Videos
  • Most relevant
  • Most popular
  • Most recent

No articles available

No slideshows available

No videos available

By using the site, you consent to the use of cookies. For more information, please see our Cookie policy.