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Planted Aquarium Substrate

substrate is the foundation of a planted tank

substrate is the foundation of a planted tank

Planted Aquarium Substrate

by Richard brown

Substrate is the foundation of a thriving planted aquarium. A mixture of sand and gravel gives makes an excellent soil, for aquatic plants to grow in. Aquatic planting media enhances growth by holding nutrients for slow release. Rocks can help keep a sloped and varied substrate thickness. Aquarium substrate is important for plants and form the basis of the general look of an aquarium.

Most aquatic plants grow roots. These roots do more then absorb nutrients. Plants release oxygen through their roots during the day. They then reabsorb some of it at night, to recharge for the next days photosynthesis.

Water is a low oxygen environment by its nature. Oxygen mixes with water about as well as oil. This is because water is a polar substance; while oil and oxygen are non-polar. Some oxygen will dissolve into the water. Plants with buried root structures can save oxygen by trapping it under the substrate in small bubbles. These tiny bubbles is what the plant breathes at night. Many aquatic plants can survive on the small amount of oxygen dissolved in the water, but if they have roots they will grow faster in when planted in the substrate.


All sand is not the same. It is best to use aquarium sand that is available at most pet stores. Commercially available aquarium sand is graded for type, size, and color. It is also free of unwanted bacteria and parasites.

Sand that is commonly used in child play grounds, called play sand, is too fine. Fine sand compacts when it becomes wet. Its very difficult to build a same castle with dry sand. If you do manage the feat the sands has to be extremely fine. Aquarium substrate has to breathe. Gases have to be able to pass through it. When sand compacts it seals gases underneath it. Bacteria feeding on decaying organic material exhale Carbon Dioxide (CO2). If the CO2 created is trapped, under or in, compacted sand it will form Carbonic Acid (H2CO3). Carbonic Acid is an extremely strong acid, only comparable to Sulfuric Acid (H2SO3). Allowing Carbonic Acid to form is the equivalent of adding battery acid. Carbonic Acid will kill everything in your aquarium.

Silica sand is used in sand blasting. Being extremely rough with small sharp edges, silica sand is ideal for removing paint, rust, residues, and coatings from metal surfaces. These abrasive qualities make it unsuitable for use in aquariums. Fish often rub against the substrate, and silica sand will damage their scales or skin. Damaged scales or skin invite diseases and infection. Bottom feeding fish will pass sand through their gills as they feed. Silica sand will cause scare tissue to develop in a fishes gills. Gill scar tissue makes it difficult for fish to breathe, and will eventually kill the fish. Besides being lethal to fish, silica sand will cause scratches in the glass or acrylic.

If you choose to source your sand from outside, here are a few thing you should do. If you can make a sandcastle with it, it is to fine. The sand will have dirt, dust, rocks, and debris mixed in with it, so it must be sifted and rinsed. There will be bacteria in it and may have parasites, so the sand must be boiled. Avoid collecting from places that likely have toxic contaminates. If people are advised not to eat the fish from the area, the sand is likely contaminated by toxins.


Gravel is a loose substrate. The best gravel is available at pet stores. Gravel will hold some oxygen and is ideal for allowing root systems to develop. Rhizome plants like anubias', ferns, and mosses can have their 'roots' or rhizomes, planted directly in it. For most applications it is better to have a layer of sand over the the gravel..

To prevent abrasions from developing on fish the gravel must be smooth. Rough gravel will cause damage to the bellies of fish, especially bottom feeders. When fish have damaged scales or skin, diseases soon follow.

If you are collecting gravel from outside there are a few thing you need to be aware of and do. Crushed rock should not be used. Crushed rock is rough and has many sharp edges. If the gravel is porous, it may be ruble from volcanic rock, you should test it with vinegar. To test rocks or gravel with vinegar, simply pour a few drops on to it and see if it bubbles. If the rock is chemically active the vinegar will bubble, and not be used in an aquarium. Gravel sourced from outside will have dust, debris, bacteria, and possibly parasites. It will have to be sifted, and boiled.

Aquarium Planting Medium

Aquarium planting medium is excellent at holding nutrients for slow release. Aquarium planting medium is usually small hardened clay beads, the good stuff is a little more complex. When root tab fertilizers are used, the substrate will be nutrient abundant for a short period of time. The clay beads will absorb these nutrients when they are abundant, and then slowly release them. This action will allow plants to absorb more of the fertilizers, and flourish.

sloping makes the sene look deeper

sloping makes the sene look deeper


Rocks can be used to create retaining walls that help keep a varied substrate thickness. Rock retaining walls will need to be tightly fitted so that the raised substrate will stay behind them. These walls are never perfect some sand and/or gravel will slip through the cracks. They can be made more efficient by placing pieces of non-biodegradable plastic behind them. Even then sand and gravel will spill over for any one of a hundred reasons. This is the imperfect method that is commonly used.

If collecting rocks from out side, rinse and boil. If the rock has a bucnch of holes in it (porous), it might be chemically active; Do a vinegar test.

Help with Basic Design

The substrate is also the foundation for the design of your aquarium. Plants and large rocks are easy to rearrange, but rearranging the substrate is difficult. Starting off with a versatile and aesthetically appealing substrate, will help remove a lot of headache in the future. A slope will make your aquarium look deeper. Varying the substrate thickness through the length will make your aquarium more appealing to viewers. Making mounds also gives a place for plants that have extensive root systems.

Aquarists use the word depth like a cabinet maker would. Depth is not how tall your aquarium is, it is referring to the distance front to back. Giving your aquarium substrate a slope, from front to back, will make it seem deeper then it really is. When an aquarium looks deeper, it will help create the illusion of a window looking out instead of in.

The rocks can be used to hold large mounds, that aren't the same size, on either side of the tank. This should create a valley, that is slightly off center, in the middle of the aquarium. The planting medium should be placed at the bottom of the mounds. You can use a fine mesh bag to prevent it from mixing with the sand and gravel. A layer of gravel can be used to fill the remaining area behind the rock walls. Finish with sand.

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Eiddwen from Wales on April 04, 2013:

Oh so very interesting;voted up.


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