Freshwater Aquarium Substrate Types
There are a lot of different options when it comes to choosing a substrate for your aquarium. This article is a simple overview to help you understand and choose between some of the options. I will look to cover both the pros and cons of each.
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Gravel
Pros
Gravel is probably the most common aquarium substrate among hobbyists. And it’s popular for good reason. It is versatile and has multiple use cases.
For one, gravel is an inert substrate. Which means that it should not affect water chemistry much. Gravel will also not break down over time and become unusable, as will some of the others. Both of these combine to give you uses for just about any inhabitant. Another perk of using gravel is that it comes in just about any shape and size you can think of. This once again provides a lot of flexibility in its use.
Gravel has some benefits for plants as well. It allows plant roots to grow without much restriction, and it is heavy enough to hold the plant down.
Cons
There are not a lot of cons to using gravel. But there are a few things worth mentioning.
One in particular is the fact that gravel will allow food and waste to fall down into it and make it difficult for the filter to pick it up or for fish to feed on. On the other hand, this could be considered a positive if you want to feed plants and hide the waste.
A second negative is the fact that it can be hard to clean. Larger gravels can show off algae, and colorful gravels can start to fade over time. I personally like a natural gravel color and don’t mind algae growing on mine. But to each their own.
Sand
Pros
Sand is really popular amongst hobbyists as well. It comes in a few different sizes and colors, with “natural” probably being the most popular.
Sand, in my opinion, is a great decorative addition to a substrate. It looks great and can keep waste from getting stuck in it. Algae shouldn’t grow too much on it, but it may not be as bright as when you first bought it.
Another great use for sand is if you have specific animals that enjoy using it. Corydoras and Geophagus are two specific species that seem to enjoy sifting through the sand.
Cons
Sand looks great, but it has a few problems to keep in mind. First of all, sand is not the best for growing plants. It tends to compact and not allow roots to grow as easily. Another issue I run into regularly with sand is the fact that it easily gets moved around the tank. Fish, filters, air, and cleaning can all stir it up. A last reason you may not want sand is the fact that it keeps waste from getting down into it. This can be a positive, as mentioned above, but it can also become an eyesore if not kept up with.
Aquarium Soil
Pros
Aquarium soils have gained a lot of popularity lately with the increase in planted aquariums and shrimp tanks. Soil can also give a natural look to the aquarium that some will like.
One of the big advantages is certainly that it has a lot of nutrients in it that plants can use to help grow, and another is that many soils will help lower the PH in a tank. A lower PH can be very beneficial for some species of fish and shrimp. Caridina shrimp are a good example of this.
Cons
Aquarium soil is actually one of my least favorite substrates in most tanks for a few reasons. First of all, you will need to replace the soil rather shortly, due to nutrients getting depleted by the plants. This can vary depending on the soil and how many plants you have. A workaround can be using aquarium fertilizer tabs when plant growth slows down.
Another thing about soils that I don’t like is the fact that when they start breaking down, they can begin to turn into powdery dirt. This can be a pain to clean and can stir up into the water column easily.
One last reason aquarium soil can be difficult to use is the high nutrient levels. Some soils will leach ammonia into the water when initially placed into the tank. This, in turn, can cause unwanted algae blooms.
Garden Soil or Organic Potting Soil
Pros
I don’t believe garden soil is a super popular option for most hobbyists, but it does have a following. The reasons many like it, from what I can tell, are the facts that it is packed with nutrients and is really cheap. Both are true. It is also true that plants can grow really well in it.
Another reason some may like it is if they are going for a super natural tank. Soil is about as natural as it gets. However, if you would like to use soil, make sure it does not have any chemicals/unnatural fertilizers added.
Cons
Soil’s main advantage, high nutrient levels, is also one of its biggest downsides. High nutrient levels can bring bad algae swings and cloudiness to the water.
Another con to soil is the fact that it can be super messy. You could be waiting for a long time for the water to finally settle out, and a fish may decide to kick it right back up again.
One last reason you may want to be careful with soil is the fact that if you get it from somewhere like your yard, you don’t know what may be in it.
Crushed Coral or Aragonite Sand
Pros
Crushed coral and aragonite have very specific use cases in the freshwater aquarium hobby. They are very good at bringing the harness of your water up and buffering it. This is great if you are keeping a fish or shrimp that likes hard water. Cichlid tanks would be a good example of a use case.
Cons
Both crushed coral and aragonite generally come in one color, white. Sometimes you can find some other colors for argonite, like black. However, if you don’t want a sterile white color, you may want to try something else.
Pro Tip: If you want the benefit of crushed coral and argonite without the looks, you can put some in a bag and add it to your filter.
Bare Bottom Aquarium or No Substrate
Pros
Yes, you do not have to have a substrate in your aquarium. In fact, some prefer not having one for various reasons. This could include ease of cleaning, a quarantine tank, or simply liking the look. All are valid reasons.
Cons
There are not really any strong reasons for not having a substrate. But a few cons that could be given are the unnatural look of the tank, the lack of planting locations, and the lack of surfaces for beneficial bacteria to grow. Also, some fish like to have a substrate to hide in or sift through.
Aquarium Substrate Types - Mixed
There are a lot of different options to choose from, but one of my favorites is simply combining a few that you like. This can help offset some of the cons of a few of the options.
Potting Soil and Sand
Capping a potting soil with sand is one of the most common ways to use soil in an aquarium. It can help cut down on the soil getting kicked up into the water and the leaching of nutrients. A thin layer of soil can go a long way.
Gravel and Sand
Mixing sand and gravel is very common. This can allow you to have places to plant plants and still allow you to have a nice sand area.
Aquarium Soil and Sand or Gravel
One really clever way to use aquarium soil is to put it in mesh bags and cover it with gravel or sand. This cuts down on the cons of aquarium soil and gives you the aesthetics of gravel or sand.
Crushed Coral and Sand or Gravel
Mixing crushed coral into gravel or sand can give you the benefits of buffering and give you an aesthetically pleasing look of sand or gravel.
Conclusion
There are a lot of brands and options out there. I didn’t cover everything. For instance, some people like to put tiles in their tanks, which can look pretty cool and be easy to clean.
But with all of this said, I want to encourage you to get what is best for you and your fish. If you like pink gravel, go for it. If you like no substrate, go for it. Just make sure your animals are happy and healthy. Thanks for reading.