Turtles Need Calcium What Dont Know main

Calcium is one of the most important minerals for your turtle’s health. A lack of it can cause quite a few health problems. Here’s what you need to do know about turtles and calcium.

Do Turtles Need Calcium?

Turtles absolutely need calcium. Consuming enough calcium is one of the most important things a turtle needs to do in order to stay healthy. Contrary to what you may think, captive turtles are usually the ones that suffer the most from a calcium deficiency as opposed to those in the wild, which generally manage to get enough calcium through their diet one way or another.

Although your turtle needs a wide-range of vitamins and minerals, there are 3 that are of particular importance:

  • Calcium
  • Phosphorous
  • Vitamin D3

All 3 of these vitamins and minerals are interlinked and play an important role in your turtle’s health. Basically:

  • Turtles need calcium for their bones, shell as well as muscular function (and more).
  • Phosphorous is needed for their bones and shells as well.
  • The vitamin D3 (which their body creates when they receive UV-B light) is needed for turtles to absorb the calcium they ingest.

How To Give Turtles Calcium?

If you feed your turtle a variety of vegetables, protein pellets and some snacks such as ghost fish or shrimp every now and again, chances are your turtle is getting everything it needs.

Except for calcium.

Turtles need quite a bit of this stuff, and there is a good chance that your turtle isn’t getting enough.
Here is how to ensure that your turtle will get enough.

Calcium Release Blocks

The easiest way to give your turtles calcium is with a Slow-Release Calcium Block. All you have to do is stick the block in the water and that’s it. It also helps condition the water. You can click the photo below for more info.

If you don’t have an aquatic turtle, you should check out my list of the best box turtle calcium supplements.

Turtles And Kale

Any meat that your turtle eats will contain calcium, but for most turtles, they probably won’t get enough of it just from protein sources alone. Leafy green vegetables and kale, in particular, are chock full of calcium and are a very healthy food for turtles. Most red-eared sliders seem to love the stuff. Ideally, vegetables such as these should be given or fed on a daily basis.

Turtles And Crayfish

Crayfish should not be fed daily to turtles, but they are great sources of calcium, as is any other crustacean with its shell intact. Other sources of calcium-rich food are roaches and crickets, but you’ll need to use a calcium supplement with those. Earthworms are often advised as well, however, they are very fatty, so should be given sparingly in my opinion.

Turtle Feeder Fish

In my opinion, the most popular types of feeder fish for turtles, such as fathead minnows, can be dangerous for turtles, as they either offer low nutritional value or contain thiamine.

However, some species can certainly boost your pet’s calcium level. In particular: killifish, guppies, mosquitofish, bluegills, bass, and guppies. All of those are good, especially if they have been raised in outdoor ponds or lakes where they were able to consume insects and other foods full of calcium.

One of the easiest methods to increase your turtle’s calcium is to provide a calcium supplement. A phosphorus-free calcium supplement in particular.

As this is usually a powder, most pet owners don’t know how to give this to aquatic turtles, because if you simply sprinkle it on their pellets, and then put the pellets into the water, all that calcium will just dissolve and disappear into the water.

The correct method is this:

  1. Put your turtle’s food into a plastic bag.
  2. Add a bit of water to the food, just enough to get it moist, but not enough to start dissolving it.
  3. Add a few scoops from a calcium supplement.
  4. Shake the bag around to get the calcium INTO the pellets and then let it dry.
  5. Feed your turtle.

This will keep the calcium stuck to the food when you put it into the water. At least long enough until your turtle eats it.

How often should you provide a calcium supplement such as this?

For a fully-grown turtle, once a week should be perfectly sufficient. If you have a tortoise, you should check out the best calcium supplements for tortoise.

Turtles And Cuttlebone

A cuttlebone is a white, chalky shell that pet owners give to their birds to nibble and peck at in order to boost their calcium intake. What a lot of owners do is to break the hard-backing off (turtles can choke on this part) of the cuttlebone, and either toss the entire thing in or drop a piece or two in and let the turtles nibble on them.

These are some of the absolute best calcium supplements to give to aquatic turtles for a few reasons:

  • The turtles can nibble and peck at them as often or as little as they want when they want.
  • They are extremely easy to prepare. You literally just drop them into the tank.
  • They usually last a while, at least a week or 2.

You can buy a cuttlebone here.

There are a few downsides, however:

  • Some turtles are quite picky and won’t touch them.
  • If left uneaten, it can fall to the bottom and dissolve in the tank, leaving your tank cloudy or with bits of calcium floating around.

My advice would be to at least try one. They are very inexpensive and if your turtle doesn’t like it, you can use the calcium powder method above instead.

Best Calcium Supplement For Turtles

My favorite calcium supplement is:

  • Zoo Med Turtle Bone (click to learn more on Amazon)  – This is my favorite calcium supplement for aquatic turtles. They are designed for turtles, and most aquatic species love to nibble on them as a source of calcium. The downside is that in some tanks, bits and pieces will fall to the bottom and may cloud your tank.

There are other calcium supplements, such as tablets or blocks that you drop into your tank, let dissolve and the calcium is then absorbed into your turtle’s skin and shell. However, I have read a lot of conflicting information as to whether this is an effective form of supplementation.

Since the jury is still out, I would simply stick to the above-listed calcium boosting foods and supplements.

Now that you know why calcium is important, this naturally begs the next question:

How Much Calcium Do Turtles Need?

In A Study of Calcium Requirements of Red-eared Slider Turtle from the Journal of Zoo Animal Medicine, 24 red-eared sliders were fed different amounts of calcium each day. At the end of the study, the authors recommended that about 2% of a red-eared slider’s calcium diet should be made up of calcium per day.

So, how do you go about making sure that 2% of your turtle’s daily intake is calcium?

The best way to answer this question, in my opinion, is this:

To offer your turtle foods rich in calcium as well as a calcium supplement and if your turtle is showing signs of a calcium deficiency, it means your turtle isn’t getting enough in its diet.

Turtle Calcium Deficiency

A lot of turtle owners believe that their pets will receive enough calcium simply through their diet.

In my experience, most people are probably not giving their turtles enough.

The problem with this is that it is extremely difficult, if not nearly impossible, to know for certain just how many milligrams of calcium your turtle needs. Far better to simply provide foods rich in calcium as well as a supplement and watch for signals of calcium deficiency.

Here is how to do this. If your turtle doesn’t receive and metabolize enough calcium over a long enough period of time, it will develop metabolic bone disease. The symptoms are:

  • Swimming or walking awkwardly
  • Lack of appetite
  • Turtle shell pyramiding (where the scutes start to develop strangely, resembling a pyramid)
  • A soft or rubbery shell
  • Swollen areas or lumps on the head

It is also important to feed a tortoise a lot of calcium to prevent pyramiding in their tortoise shell.

Both pyramiding and MBD can also be cause by regularly feeding your turtle fish food.

Metabolic bone disease isn’t the only thing however that you need to watch for.

Problems Associated With A Lack of Calcium

Calcium-deprived turtles can also develop anorexia. This happens because calcium is needed not just for a turtle’s shell and bones, but also to properly contract its muscles. Without enough calcium, the muscles and digestive process in a turtle’s gut slow down, and the turtle begins to eat less and less. Eventually, significant weight is lost.

In hatchlings, turtles can develop a type of condition where their shell does not develop properly due to a lack of calcium. What will happen is their shell will develop abnormally, as in, it could be lopsided or uneven. In pregnant turtles, a lack of calcium can lead to her being egg-bound, which means that she is unable to move her eggs outside of her body.

Now that you know calcium is critical for a turtle’s health, I want to explain just how to give it to your pet.

How Do Turtles Get Calcium In The Wild?

Most wild turtles are able to get enough calcium through the consumption of certain wild plants, vegetables, and insects. Usually, they aren’t quite quick or agile enough to chomp down on fast-moving fish or crayfish.

A common perception among pet owners is that their diet in captivity is much better than what they would get in the wild. And while that may be true for most pets, I have found that it isn’t often the case for turtles.

Here’s why.

Most turtle species are carnivorous opportunists masquerading as omnivores. What this means is that most turtle species much on plants, vegetation and easy to capture insects and other prey, but will jump at the chance to eat a crayfish, shrimp or fish.

Basically, they will try to eat anything. Especially anything that moves.

Because of this, a lot of pet owners mistakenly believe that because their turtle jumps at the chance to munch on something (usually pellets), that that is all it needs.

And while pellets have a lot of minerals, vitamins, and nutrients. Pellets by themselves aren’t enough.

Remember when I said that there are 3 vitamins and minerals in particular that turtles need?

  • Calcium
  • Phosphorus
  • Vitamin D3

What Do Wild Turtles Eat?

In the wild, turtles don’t simply eat one type of food. They don’t just munch on kale. Or turtle pellets.

Instead, they consume a wide variety of plants, vegetation, insects and other easy-to-catch prey. That, combined with them receiving enough vitamin D3 through basking, as well as the fact that they often are able to ingest enough phosphorous through plants and vegetables, means that a lot of wild turtles actually have a fairly nutritious diet.

On the other hand, even if you are offering your pet turtle enough calcium, it may not actually be metabolizing the calcium it does receives for 2 primary reasons:

  • Your turtle isn’t receiving UV-B rays.
  • Your turtle is consuming too much phosphorus relative to the amount of calcium it is receiving.

The first cause is easy to solve. Get a UV-B producing bulb, make sure you set-up the proper distance and temperature, and let your turtle bask.

The second problem is also rather easy to fix. Use a phosphorus-free calcium supplement or a Turtle Bone. This will ensure that your turtle’s calcium level always exceeds its phosphorus level.

Ideally, the calcium to phosphorus ratio in your turtle’s diet should be somewhere between 1:1 to 2:1 (2 parts of calcium for every 1 part of phosphorus).

Although phosphorus is a critical mineral, it binds to calcium and doesn’t let it fully absorb inside turtles’ bodies. This is why you always want to keep your turtle’s calcium level above its phosphorus level.


  • Turtles absolutely need calcium in order to be healthy, along with phosphorus and vitamin D3.
  • If a turtle is deprived of calcium long enough, it can eventually develop metabolic bone disease.
  • The best way to ensure that your turtle is receiving enough calcium is through offering things such as kale, the occasional crayfish and feeder fish but more importantly, a calcium supplement such as a Turtle Bone or cuttlebone.
  • Without access to UV-B light, your turtle’s calcium supplement intake will be largely wasted.
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