» Posted by on Nov 5, 2015 in Blog, Education, Freshwater Fish, Kristen S | Comments Off on The pH of Your Freshwater Aquarium

The pH of Your Freshwater Aquarium

Kristen Schmicker


One of the water parameters that we like to test here at the store is the pH of the aquarium.  The higher the pH the more basic the water is.  This may also be referred to as having hard water which means there are a lot of dissolved minerals present.  The lower the pH the more acidic the water is.  This is usually soft water which is lacking dissolved minerals.  In general, the ideal pH of a community aquarium should be around 7.0 on the pH scale which many fish species prefer.  There are species of freshwater fish that thrive better in an aquarium that has a lower or higher pH.  Some fish tolerate a large range of pHs so you don’t have to monitor the pH as closely but for other species the required pH should be maintained and only fish with similar pH ranges should be added to the aquarium.  Below is a chart of common freshwater fish and their ideal pH ranges.

Lower pH Wide Range (6.0-8.0) Higher pH
Rasboras (5.8-7.0) Barbs Blind Cave Tetra (7.5-9.0)
Loaches (6.5-7.5) Danios Mollys, Guppies, Platys & Swordtails (7.0-8.5)
Hatchetfish (5.5-6.5) Sharks & Minnows Rainbowfish (7.0-8.0)
Glowlight Tetras, Head-and-Tail-light Tetras, Rummynose Tetras, Serpae Tetras, Black Neon Tetras, Lemon Tetras & Red Phantom Tetras (5.5-7.5) Bloodfin Tetras, Black Skirt Tetras, Silvertip Tetras, Buenos Aires Tetras, Neon Tetras & Emperor Tetras S.petricola & S.multipunctatus (7.5-9.0)
Cardinal Tetra (4.6-6.2) Corydoras African  Rift Lake Cichlids (8.0-9.0)
Synodontis sp. (6.5-7.5) South American Cichlids (7.0) Freshwater Puffers (7.5-8.5)
Plecos (6.0-7.5) Kribensis
Apistogramma sp. (6.0-7.0) Angelfish
Rams (5.0-6.5) Bettas & Paradisefish
Discus (6.5-7.0)
Gouramis (6.5-7.0)


Changing the pH of your tank to suit the needs of your fish can be pretty simple assuming your water chemistry is good.  The first step is to test the pH of the water you are using to fill your tank.  If you are using hard tap water and you want to lower it, you can use a Neutral Regulator buffer or an Acid buffer depending on how high the pH is and how much you want to lower it.  You could also use Reverse Osmosis water, which usually has a pH in the 6.0 range.  Adding a piece of driftwood to the aquarium can also lower the pH.

If the pH of your water is too low you can try a buffer like Neutral Regulator or Alkaline Buffer.  You can also use crushed coral, Texas Holey Rock, or salts for African Rift Lake Cichlids or Rainbowfish.  Low pH can also be a result of a dirty gravel bed or a dirty filter especially if you have high nitrates.  A good gravel vacuum and water change or filter cleaning can raise the pH back up.

Changing the pH of a freshwater aquarium varies greatly from tank to tank.  If you’re interested in checking or changing the pH of your aquarium to suit your fishes’ needs or you’re not sure what your pH should be at, come on in to the store and we’ll help you get started!


Reference:  Sweeney, M.E. (2009) Tropical Fishes. Neptune City, NJ:  T.F.H. Publications

Copyright 2013 Absolutely Fish, Inc. All Rights Reserved