Why Is My Turtle’s Shell Soft? (How to Solve and Prevent)

Strong shells are essential for a healthy turtle, whether it lives in a tank or in the wild. If you find your turtle’s shell is soft, it means that it’s suffering from metabolic bone disease.

A soft shell is usually caused by metabolic bone disease, which is caused by a diet that lacks calcium, or by poor lighting, which can prevent the proper absorption of calcium. Without enough calcium, the shell of a turtle can become soft.

So the problem is either the lack of calcium or the lack of UVB light, which allows turtles to process the calcium. Luckily both problems are quite easy to solve. So let’s see how you can do that.

Calcium Prevents Soft Shells

There are three main ways in which a pet turtle can get calcium, the first one is through vegetables, the second one is through supplements like cuttlebone and calcium powder, and the third one is by eating fish. And each one of them has its own advantages and disadvantages.

Calcium From Vegetables

Vegetables are an amazing food, they have a lot of vitamins, they have fibers, and they have calcium, it might seem that there is no downside to them. But there is one,  and it’s quite big, and that disadvantage is that they have phosphorus.

Phosphorus is what gives turtle shells flexibility, which is great because this little extra flexibility makes them more resistant to bites and other types of impact. But too much phosphorus can also make the shell a lot softer, and fragile, which is not good, even if there are no predators to take advantage of this weakness of the shell, it will affect the overall health of your turtle.

Most vegetables have a calcium to phosphorus ratio, this ratio can be 1:1, 2:1, 5:1, 1:2, etc.

A 1:1 ratio means that the amount of calcium is equal, or almost equal to the amount of phosphorus. So a vegetable with this ratio is not that great for turtles, but it’s not harmful either. But if possible such a vegetable should be avoided.

A 1:2 calcium to phosphorus ratio is really bad, there are not many vegetables with this ratio, so don’t worry too much about them. Just remember that if a vegetable has more potassium than calcium you should keep it away from your turtle.

A 2:1 ratio is great, and this is what you should be aiming for, if the ratio goes higher it’s ok, but ideally this is the ratio that you are looking for.

At the end of the article, I will post a table with some of the most common vegetables that you will find in a supermarket and their calcium to phosphorus ratio.

Calcium From Fish

Turtles love fish, if they could they wouldn’t eat anything else, and this is not a bad thing since fish have a lot of calcium and nutrients. But the problem is that not all fish are good for a turtle, in fact, most of them are quite dangerous.

Some fish contain too much fat, some of them have sharp bones that can hurt the insides of the turtle, and so on. So, there are very few fish that your turtle should be eating.

Here is a list of the fish that your turtle can safely eat:

• Bluegills
• Bass
• Crappies
• Guppies
• Killifish
• Platies
• Mosquitofish

If you want to know what other types of fish your turtle can eat, and more importantly which one you should avoid you can check out this article where I discuss the subject more in-depth: Feeder Fish For Turtles (Beginners Guide + List).

Calcium From Supplements

Giving your turtle vegetables and fish is a great way to increase their calcium intake, but in most cases, this is not enough, and you should also give them some supplements.

The most common types of supplements are cuttlebone and calcium powder.

For cuttlebone, I have a dedicated article which you can find right here: Cuttlebone for Turtles (Beginners Guide + Buyers Guide). Some of the key points are:

• Remove the back part of the cuttlebone
• Break the cuttlebone into pieces that are the same size as the head of your turtle
• You should give your turtle cuttlebone once every two weeks
• Cuttlebone comes from fish, so all cuttlebone is the same

Overall cuttlebone is a good choice, the only problem that can arise from it is that your turtle won’t eat it and over time the cuttlebone can dissolve in the water and make the water hard.

If your turtle doesn’t show any interest towards the cuttlebone, then you still have one more option, calcium powder. Calcium powder, just like cuttlebone, is a supplement. But the way you use it is a little bit different.

The best way that I’ve found to use calcium powder is to take a plastic bag, put some calcium powder in it, add some pellets, and then add some water, so the calcium sticks to the pellets, and then feed the pellets to the turtle one by one. The reason why you don’t want to give your turtle all the pellets at once is that the calcium will quickly get off the pellets, and most of it will end up in the tank.

If you look for calcium powder for reptiles you will notice that there are two types, one with vitamin D3 and one without D3.

Vitamin D3 allows your turtle to assimilate and make use of the calcium that you are giving it. Without D3 all that calcium won’t do anything. D3 usually comes from the sun, or from the basking area, in the case of pet turtles.

So even if you get calcium powder with D3, you still need to make sure that your turtle has a proper basking area from where it will get all the D3 that it needs.

Vitamin D3

Turtles get their D3 from the basking area, which should be equipped with two light bulbs, one that provides heat, and one that provides UVB light.

The UVB bulb is the one that replicates the effects of the sun and provides vitamin D3 for your turtle.

Both bulbs are very important for the health of your turtle and need to be placed in a certain way in order to be effective. If the bulb is too far, its effects will be diminished. If the bulb is too close it can lead to burns or other health problems.

In the article Best Turtle Light Bulb (Illustrated Buyers Guide) I have an In-depth guide on how to choose the correct wattage and how far you should place it from your turtle. Here is a short extract about the UVB bulb, the one that is responsible for vitamin D3.

When it comes to choosing UVB bulbs things are a little more complicated due to the huge variety of wattages, in which UVB bulbs can be found. And then there is the fact that most manufacturers have a different rating system, and some of them have no instructions at all.

So, for UVB bulbs, I am going to give you the exact distance for a few bulbs that I’ve used before that come from a reputable manufacturer, and I will provide links to Amazon, where you can get them

And in case you have something between the UVB bulb, like a net, or a grill, you want to move the bulb closer by one inch, as anything in between the turtle and the bulb will reduce the amount of UVB rays.

One more thing to keep in mind is that UVB bulbs will stop producing UVB rays, way before they will stop producing light. On average I would say that a UVB bulb only produces UVB rays for only half of its lifespan. I measured the amount of UVB light produced by the bulbs and noticed that after about 6 months, the amount drops considerably, so I change my light bulbs at around 6 months, and I would advise you to do the same.

And if you want to measure how much UVB light your bulb produces you can use this device. While it’s a little bit expensive, overall it will save you money since you will know exactly when the bulbs run out of UVB light, and it will help your turtle remain healthy. But it’s not a requirement.

Calcium From Pellets

One more thing, regarding food, that I want to mention is that most pellets have some calcium in them, but that amount is usually quite small, so while it’s good that it’s there, it’s not enough.

So just because the pellets have calcium in them, doesn’t mean that they have all the calcium that your turtle needs, and that you shouldn’t give your turtle more.

Can You Give Your Turtle Too Much Calcium?

Technically speaking too much of anything can be dangerous, so yes you can give your turtle too much calcium, but practically speaking you would have to give your turtle absurd amounts of calcium in order to affect its health.

As long as you don’t go overboard with it, there should be no problem.

How Much Calcium Should I Give My Turtle?

There is no set amount of calcium that you should give your turtle. As I said the main thing that you should be careful of is not overdoing it.

Here is how I give my turtles extra calcium.

I feed my turtles a small amount of vegetables once every two weeks, and 2 fish once per month. And once every two weeks I give them a small piece of cuttlebone. For the turtles that don’t like the cuttlebone, I use calcium powder. All this while giving their regular meals (pellets) once every 3 days.

The only time I skip giving them pellets is when I give them fish, as the fish should be more than enough to replace the pellets.

I’ve been doing this for quite a few years, and my turtles are as happy and healthy as they’ve ever been. So I would recommend you to try this routine or a similar one.

Final Thoughts

A soft shell is caused by a lack of calcium, so the best way to treat and prevent is to make sure that your turtle has enough calcium in its diet and that it can properly use it.

There are multiple calcium sources: vegetables, fish, and supplements. And it’s a good idea to combine them, and not rely on a single one, since each of them has multiple health benefits, aside from providing calcium.

And don’t forget that calcium on its own won’t do anything, turtles also need vitamin D3 to properly assimilate and use the calcium. Vitamin D3 comes from the sun, or in the case of pet turtles, from the basking area. So make sure that your basking area is in order, otherwise, all the extra calcium won’t do anything.

And I would also advise you to go visit a vet with your turtle. A soft shell is definitely not a good thing, and while doing everything in this article should solve the problem and prevent it from happening, there is a possibility that the problem might be more complicated than this, so it’s better to be safe.

I hope that this article answered all of your questions, but in case there is anything else that you would like to know, don’t hesitate to use the comment section below, and leave your question there. I will answer it as soon as I see it.

Here is a list of some of the most common vegetables and their Calcium to Phosphorus ratio:

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