Goldfish Aquarium Gravel Substrate

Goldfish Aquarium Gravel Substrate

A goldfish aquarium doesn’t need a gravel substrate but the goldfish in that goldfish aquarium surely would appreciate it. Not only is a gravel substrate aesthetically pleasing, it creates a place for beneficial nitrifying bacteria to grow. A quarter to two inch (1-5cm) layer of gravel substrate designed for use in aquariums increases the biological filtration of a goldfish aquarium. Even a quarter inch of gravel will allow beneficial nitrifying bacteria to grow. An aquarium gravel substrate of more than two inches can contain pockets of low oxygen and encourage the growth of harmful bacteria that produce gasses toxic to goldfish. Two inches or less of an aquarium gravel substrate also makes it more manageable to clean.

Types of Substrate

  • Aquatic Plant Substrate
  • River Sand
  • Fine Gravel
  • Medium Gravel
  • Colored Gravel
  • Coarse Gravel
  • Small Stones
Aquarium gravel substrates have a way of trapping dirt and debris and keeping it from floating free in the goldfish aquarium water. If large particles find their way into the gravel substrate, they are less likely to disintegrate and turn the goldfish tank water cloudy. Using an aquarium gravel siphon, pollutants in the aquarium gravel are easy to eliminate from the goldfish aquarium. Every goldfish aquarium, gravel substrate or not, is going to need routine maintenance including cleaning the bottom of the tank.

Cleaning the aquarium gravel substrate might be a bit more difficult if it is used to anchor and root live aquatic plants. Some aquatic plants need to be anchored into a substrate in order to grow. There are aquatic plants that get their nutrients from the substrate itself or from the tank water. Depending on the growing requirements of an aquatic plant, the type of substrate in which it grows will vary. Many aquatic plants that are suitable for goldfish aquariums get their nutrients from the water and not the substrate.

Pebble Substrate

The Ideal Option for Goldfish

By nature, goldfish are scavengers and will feed off the bottom of a goldfish tank. A goldfish that is searching for food will often poke around in the substrate by moving around the pieces of substrate. If the substrate pieces are small and round enough, the goldfish might pick it up in its mouth and then spit it back out again. Goldfish do a good job of removing excess food off the top layer of substrate. This goldfish behavior eliminates aquatic plant substrate, river sand and small stones as an option, Goldfish will kick up sand and plant substrates when they dig at the tank bottom. This digging can cloudy the tank water and clog the filter and filter media. The small stones are too large for the goldfish to move around, not allowing them to eat the food that might be trapped between the stones.

The best goldfish aquarium substrate is a medium to small size rounded gravel. This gravel should be inert a doesn’t leach chemicals or colored dyes into the goldfish tank water. It’s easy to avoid using an aquarium substrate that leaches if the packaging clearly states ‘for use in aquariums’. It can be risky to use gravel, sand or stones from natural sources since it can leach pollutants or calcium which can throw off the pH in the goldfish tank water. Always rinse new gravel to remove dust before placing it in a goldfish aquarium.

Reviewed By: Tim Winter

Tim Winter has a strong affection for pets and wildlife. His years of experience caring for various types of pets has led him to share his knowledge with others on the best practices in pet care. Tim holds a Bachelor of Science from the University of Oregon School of Journalism and Communications.

9 thoughts on “Goldfish Aquarium Gravel Substrate”

  1. I was just wondering what colours goldfish like…are blue standard aquarium pebbles ok…or should i go natural brown etc? I just want it to be easy for them to find their food.

  2. Lexie, the behavior your goldfish is showing is called ” new tank syndrome” he/she was not transferred properly and is under a large amount of stress. I say buy a stress reducing a water additive, that shall hopefully work. Three of my goldfish died of this,i thought they were all fine but when ifound them deAd the next day,i asked my vet.

  3. Oh okay thank you. Also, when I put my goldfish into it’s new tank, it just sat on the bottom and didn’t swim around much. Today it’s doing the same thing and won’t eat. What should I do?

    • If you bought the gravel from a pet store, it has been washed but typically you should rinse it again to remove any gravel dust or dirt that might have made its way into the bag. Your goldfish should be just fine, if there is any dust, it should settle eventually (cloudy water will clear up).


Leave a Comment