There’s a critical decision every goldfish owner needs to make:

“What substrate do I use?”

Or perhaps,

“Do I even NEED one?”

Great questions.

In today’s post, I’m going to give you my thoughts on the different options I’ve tried over the years and which one is best for goldfish, based on solid research and my own personal findings.

Let’s get started!

Options for Goldfish Substrate Compared

Sand

Sand really is a fantastic substrate for goldfish in my opinion.

But don’t take my word for it:

This study by the Universities Federation for Animal Welfare found that sand was the best of all substrates for goldfish for foraging (they tested sand, gravel, plastic grid and cobbles):

Goldfish foraged longest when provided with coarse sand… In general, coarse sand (1.5 mm) was found to be the most appropriate substrate in terms of facilitating natural foraging behaviours. These findings are discussed with respect to the welfare and husbandry of goldfish and aquarium fish in general.

Source – https://www.ufaw.org.uk/downloads/awj-abstracts/v20-3-smith.pdf

In my book, sand has all the benefits without the disadvantages of the other common options.

Yes, sand!

  • It’s super natural.  Pond and river bottoms are often made of either silty mud/dirt or sand. (Mud is probably not a good option unless you like the “brown cloud” look.)
  • It’s fine enough so goldfish can’t choke on it
  • So easy to clean – the debris sits on top rather than getting trapped in between cracks and crevasses
  • Goldfish love foraging in it, digging around like moles in search of food
  • There are many interesting color variations to choose from

In my experience, courser sand is better than fine sand.

It really tends to get vacuumed up, clogging EVERYTHING – siphons, pumps, equipment and sinks.

That’s why I love using Caribsea Super Naturals “Crystal River” in my goldfish tanks.

Grain size is perfect and the neutral color doesn’t have a bad glare.

Another great option is Seachem Flourite sand (comes in black).

It’s ideal for planted tanks.

Gravel

This is probably the most widely used for aquariums in general.

It comes in many colors, some natural, others dyed in neon colors.

Gravel gets a bad rap for being a choking hazard for goldfish, which is absolutely true of that pea-sized gravel sold in most pet stores.

See:

Goldfish have a bigger mouth size than most fish and a fondness for pecking at the bottom and picking things up in their mouths.

Many fishkeepers have experienced their goldfish getting it lodged in their mouth or back of the throat – and many times they don’t realize what’s wrong until it’s too late.

So that’s why gravel should be at least 1/2″ to 3/4″ in size.

Now:

Don’t get me wrong:

An inch or two of gravel can look quite nice and natural at the bottom of the tank, as well as provide something interesting for the fish to peck on at the bottom.

BUT…

I really don’t recommend setting it up that way.

It’s very difficult to clean, even to the point of being almost IMPOSSIBLE to get clean (you know what I’m talking about if you’ve ever tried it).

With goldfish producing so much waste, it can be a big messy nightmare.

That said:

There are workarounds to this, and gravel can make an amazing, low-maintenance substrate – if you know how to use it right.

Read More: Gravel in the Goldfish Aquarium

Nothing (Bare-bottom)

Bare-bottom has a definite set of advantages, especially in certain situations, that shouldn’t be overlooked.

When you need as hygienic conditions as possible (such as in hospital, quarantine, breeding or fry tanks), bare-bottom is probably the best way to go.

Cleaning up the waste doesn’t get any easier.

You can always tell what’s going on “down there.”

No worries about nasties building up.

That said:

For an average goldfish aquarium without special circumstances, you don’t have to be as rigid.

In fact…

… By and large I would encourage you not to be.

For two main reasons:

1. Depriving them of Natural Behavior Expression

Here’s the deal:

Goldfish in the wild are foraging creatures by nature.

In a pond or a slow-moving stream, they would graze all day long by pecking and nudging around at the bottom for food.

(I mean, their mouth is even designed like a vacuum cleaner!)

Having a substrate really facilitates this natural behavior.

With a glass bottom, they can’t pick stuff up in their mouths and sift through it – even if they will always be trying.

Providing a substrate enhances their environment and allows them to express their natural instincts while living in captivity.

As pet owners, we should try to do everything we can to keep our goldfish happy where possible and practical.

2. More Extreme Lighting Glare

Some fishkeepers try to get around this by painting the bottom of the tank on the outside.

This might help some, but there’s still a lot of reflectivity on the glass surface.

If you keep a light on your aquarium (which you probably should), your goldfish are being subjected to this glare all day long.

Having a substrate (especially a natural-toned one) really helps absorb these extra rays and stops the harsh glare – way more than paint.

How to Improve a Bare-Bottom Goldfish Aquarium

Now, if after everything I told you, you STILL want to do a bare-bottom tank, I’m not going to judge you. ;)

But please consider a few things (unless maybe its for a hospital/QT tank):

  • Live plants – and lots of them (preferably tall ones that bend over a bit near the surface of the water) – will help shield the glare from the lights.  They also give the fish stimulation with something to swim through and peck on.
  • Foraging materials – All goldfish should have access to foraging, but you really, REALLY shouldn’t deprive your goldfish of foraging if you’re going to keep them in a bare bottom tank.  They need stimulation.
  • Company – Can you think of anything sadder than a lonely goldfish all by itself in a bare-bottom, empty tank with nothing to do all day?

Handing it Off to You

Now you know which substrates are best for goldfish.

What are your thoughts?

Have you tried something that maybe I didn’t touch on in this article?

I’m open to discussion if you have a different opinion.

Please leave your comment in the section below if you want to share a tip or leave your thoughts.