Blackwater Tanks for Angelfish

Angelfish are native to South American blackwater and clearwater streams making a blackwater tank suitable for angelfish. Blackwater enhances the colors of fish native to blackwater streams, and some angelfish breeders find it helps induce breeding. Other fish living in the Amazon Basin region include, discus, tetras, gouramis, dwarf cichlids, pmelodids, loricarids and corydoras catfish.

Blackwater aquariums are freshwater tanks set up to replicate natural blackwater stream environments. Blackwater streams and rivers, such as the native habitat of the scalare and altum angelfishes the Amazon River, contain high amounts of tannin that make the water tea colored. The source of tannin in the river and its tributaries is peat; decaying leaves, wood, roots, and other vegetation. As the streams and water flows off the Andes and into the Amazon basin, the water collects the tannins from the peat along the way. The water that finally reaches much of the Amazon basin is “tea-colored, acid, and contains little more in the way of dissolved minerals than distilled water,” reports The Complete Fishkeeper.

Blackwater Tank Chemistry

The slow moving water in blackwater streams have low water hardness and an acidic pH. Anglefish, discus, tetras and other fish thrive in acidic, soft water streams. There are several options for creating an angelfish blackwater habitat.

How to Set Up a Blackwater Aquarium

Mopani wood in the fishtank will create blackwater.

How to Set Up a Blackwater Aquarium

In the natural habitat, tannins from driftwood, leaves on the stream bottom and other decayed plant matter make natural blackwater streams.

Make blackwater for your angelfish tank  by boiling sphagnum peat moss or dry leaves, such as oak, and after filtering use the concentrate for water changes. Bring the water to a boil, then let it simmer for about 30 minutes. A starting point for using this concentrate is one quart for 25 gallons of water. Use more or less concentrate to adjust the pH.

An easier method is to use a commercial blackwater extract tonic, however that looses the blackwater effect after a time.

A finished black water tank may have leaves such as oak or almond on the bottom and heavily planted with live plants. Woods such as Mopani or bogwood provide hiding places for Angelfish and a source of tannin. Remove rotting leaves and wood as they are harmful to the fish. The final effect is a warm visual experience for the viewer, and a great environment for angelfish and other blackwater fish.

Sphagnum Peat Moss for Blackwater Tanks

Peat pellets are an easy way to create a blackwater environment.

Using Sphagnum Peat Moss for Blackwater Tanks

Using sphagnum peat moss in a mesh bag in place of the carbon filter is another way to make a blackwater aquarium. Rinse and wet the pellets or moss so they  will be clean and won’t float. Pack the moss firmly, not too loose or not too tight for best results. A carbon filter prevents the peat moss from coloring the water. If used in place of the carbon filter, it will discolor the water.

Sphagnum peat moss raises acidity and reduces mineral content to make the water softer. The bag will last about a month before it’s necessary to replace with fresh moss. The moss without additives can be purchased at garden supply and aquarium supply stores. Before using in an aquarium, rinse in dechlorinated or distilled water. Check the chemistry of your tank regularly to determine how often to change the moss.

Another method for using peat moss is to put it in a mesh bag and boil or filter water through it. Use this water for water changes. Soft water can cause the pH level to be unstable, so more frequent water changes may be in order.

Aquarium suppliers also sell peat moss in pellet form. Put peat pellets in a mesh bag and put into the filter space for charcoal. Rinse the bag and peat before putting in filter, it will help the peat absorb water quicker.

Disadvantages of Blackwater Tanks

You will need to do water changes more frequently than with a hard water aquarium. Also, a blackwater tank chemistry needs to be tested frequently because the pH can swing quickly. It’s hard to select the proper amount of peat each time, and more or less will affect the chemistry balance. It’s better to err by using less rather than too much. If you are not comfortable creating the blackwater yourself, use a commercial blackwater tonic product.

Blackwater Aquarium Plants

Many fish tank plants don’t do well in soft water. A few recommendations are Echinodorusm Vallisneria, Cabomba, and hornwort aquatic plants. Here is a list of plants that don’t necessarily live naturally with angelfish that may do well in a blackwater aquarium. Peter Hiscock’s book, Encyclopedia of Aquarium Plants is an excellent reference book about aquarium plants, planting and their care.

  • Anubias barteri
  • Anubias barteri
  • Anubias nana
  • Crinum thaianum (water onion)
  • Crinum natans
  • Cryptocoryne balansae
  • Cryptocoryne petchi
  • Cryptocoryne wendtii
  • Echnidorus bleheri (Amazon broadleaf)
  • Ozelot (Echnidorus hybrid)
  • Hydrocotyle leucocephala (pennywort)
  • Hygrophila corymbosa (temple plant)
  • Microsorum pteropus
  • Saggitaria subulata (narrow leaf sag)
  • Jungle and Italian Vallisneria


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