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A cuttlebone is one of the best calcium supplements to give to a turtle. This is what I would recommend for most turtles.

The Best Cuttlebone For Turtles

To get straight to the point, this is what I have been using with my turtles:

  • Zoo Med Turtle Bone (click to learn more on Amazon). This is the most popular cuttlebone supplement for turtles out there. Zoo Med is in my opinion, one of the more trustworthy pet turtle brands in existence, and this is basically the reason I recommend this one over more generic cuttlebones or other brands.

Here’s why I recommend this product in particular, and cuttlebones as a source of calcium for turtles.

Turtles And Calcium

Calcium is one of the most important minerals for a turtle’s health. According to a study in the Journal of Zoo Animal Medicine, red-eared sliders need their diet to be about 2% calcium in order to avoid shell abnormalities and weight loss. Moreover:

  • Calcium helps keep their bones and shell strong and healthy.
  • It helps with muscular function.
  • This supplement also helps nerves to send messages to and from the brain.

And many, many more reasons.

There is another mineral, phosphorus, that is for turtles nearly as important as calcium. What  you need to know about both of these minerals, however, is this:

  • Turtles need a certain amount of calcium and phosphorus in order to remain healthy.
  • Turtles need their calcium level to be higher than their phosphorus level.

I don’t want to make it too complicated but think of phosphorus as a kind of “canceling out” calcium. What happens is that phosphorus binds to calcium and that this binding can cause overall calcium levels to drop. Both of these minerals are vital, but turtles need just an extra bit of one, calcium.

Here’s the thing:

  • Most turtles receive enough phosphorus through a balanced diet of turtle pellets, leafy green vegetables, sparse fruits and crayfish, feeder fish, etc.
  • But most captive turtles do not receive enough calcium through their diet.

This is a big reason why I would recommend a calcium supplement for your turtle. Just to be on the safe side. 

How To Give Turtles Calcium

Now, there are 3 major types of calcium supplements that you can give to your aquatic turtle:

  • Cuttlebones.
  • Calcium powder.
  • Calcium supplements that dissolve into the water.

From what I have read, the last type, which is basically a block of calcium that you throw into your tank and let dissolve with the aim of being soaked up and metabolized by your turtle, are pretty ineffective. I also just don’t have a lot of experience with them, so for now, let’s exclude those.

That leaves 2 types; cuttlebones and calcium powder.

Calcium powder is an absolutely excellent form of supplementation. The problem is that unless you do a bit of preparation, it won’t work for aquatic turtles, as the powder will simply dissolve into the water.

This is why so many turtle owners love cuttlebones.

What is a Cuttlebone for Turtles?

A cuttlebone for turtles is actually the internal skeleton of a cuttlefish (where its name comes from). Unlike the hard, firm bones you are probably thinking of, cuttlebones are softer and chalkier. They are extremely popular among bird owners.

However, they also work really great for aquatic species of turtles, as you can basically throw it into your tank and let it sit there. Turtles, being the opportunists that they are, will swim by and nip at it, breaking it apart, eating bits and pieces of it and thus, getting their calcium.

Another added benefit of cuttlebones is that they will “flatten” out a lot of aquatic turtles sharp beaks. Personally, I haven’t really noticed this to be the case with my painted turtle and red-eared slider, but a lot of other owners have experienced this with theirs.

I have experimented with a few different types and if someone asked me to recommend them a calcium supplement for their turtle, I would give them the following answer based on my experience.

The Best Turtle Cuttlefish Bone

My favorite cuttlebone for turtles is this Zoo Med Turtle Bone (click to learn more on Amazon).

Although it’s labeled a “turtle bone” it’s basically just a regular cuttlebone that is marketed as something for turtles. It’s not. It’s the same exact cuttlebone that birds peck on.

So, why do I recommend this instead of the slightly cheaper cuttlebones that you will find in the bird section of a pet store?

The honest reason is that I simply have come to trust Zoo Med as a company. I have used and continue to use a lot of their products, and I feel that, at least in the turtle department, they make high-quality stuff.

Zoo Med’s Turtle Bone is also the most popular calcium cuttlebone supplement on the market. It has more reviews, the vast majority of which are positive, than any other cuttlebone I have seen anywhere. I’ve also seen it in one of the local pet stores where I live, another good sign.

If Zoo Med puts its label on something, I’m probably going to trust it. At the very least, I will know it is not harmful or poisonous for my turtle.

Cuttlebone Backing

Whatever cuttlebone you end up getting, there is something EXTREMELY important that you need to know. You must always remove the hard-backing on every cuttlebone before giving it to your turtle.

You should be able to immediately tell which side of the cuttlebone to feed to your turtle the moment you pull it out of the box:

  1. The hard-backing is the side that looks almost like plastic and feels very hard and solid.
  2. The other side will look whiter, less shiny but more importantly, will feel “chalky”.

It is only that chalky side of the cuttlebone that you should feed to your turtle.

How To Strip Cuttlebone Backing

Here’s how to remove the backing:

  1. Break the cuttlebone into pieces using your hands.
  2. Use a pair of scissors or a butter knife to remove the hard-backing on the pieces.
  3. Be very careful!
  4. Check each piece by digging your fingernails into it. If you can easily dent the piece, that means its the portion of cuttlebone that can be eaten by your turtle.

If you need a visual guide, I basically do the exact same thing as shown in this video:

The hard-backing absolutely needs to be removed before feeding it to your turtle. I can’t repeat this enough!

If you don’t remove it:

  1. Your turtle could possibly scratch or cut itself on it.
  2. Your turtle could possibly choke.

Once you have finished breaking it into pieces and removing the hard-backing, you are basically done at this point.

How Long Is Cuttlebone Good For?

It should last a long time. Usually, it takes my turtles about 3 to 4 weeks to go through a single cuttlebone. With other turtles, they can go through them even faster. Others are slower.

I want to also mention however that some turtles may NEVER eat them.

This is totally normal. Some turtles just won’t eat them. My advice would be to break off a piece or 2 and just leave it in your tank. What may be happening is that your turtle simply doesn’t recognize it as food yet.

The worst thing that will happen is that it will eventually fall to the bottom of your tank and slowly dissolve. Generally, cuttlebones don’t dissolve very fast, so it won’t cloud up your tank.


  • Most captive turtles are probably not getting enough calcium, and as such, most likely are in need of calcium supplementation.
  • A cuttlebone is one of the BEST calcium supplements to give to turtles.
  • Zoo Med’s Turtle Bone is probably the most popular cuttlebone supplement on the market.