Red Tail Shark Size and Growth

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If you’re into aggressive and territorial fish species, Red Tail sharks are the perfect choice as tank pets. It also helps that they’re cheap, can live up to 8 years in captivity, and are generally hardy and resilient.

But, before getting one, the first thing to note is the fish’s size. That’s because its size determines other important factors such as tank size, how many you can keep, the size of its compatible tank mates, etc.

The growth rate is another useful indicator since it tells you whether you should upgrade your tank anytime soon.

How Big do Red Tail Sharks Grow?

A typical Red Tail Shark can grow up to 6 inches in captivity, making this one a medium-sized fish by aquarium standards.

If you think this fish’s size is an indicator of how large its tank should be, you’re mistaken. The tank size for a Red Tail fish rests more on its behavior.

Red Tail sharks are semi-aggressive but extremely territorial and require at least 30 gallons of water. This is the necessary space for one fish living alone in its aquarium.

Placing 2 Red Tails in the same tank is the recipe for failure since Red Tails cannot stand each other’s presence.

The 2 Red Tail males will attack and kill each other on sight, and there’s no aquarium large enough to prevent that. Some people suggest getting a 90-100-gallon tank if you plan on keeping more than 1 Red Tail, which is already excessive for 2 6-inch fish.

You will also need to create a thorough and complex tank layout comprising multiple caves, rocks, and plants. Whatever you can to break the line of sight between the fish.

I wouldn’t recommend it anyway because, eventually, the 2 Red Tails will bump into each other. And that’s game over.

How Fast do Red Tail Sharks Grow?

The Red Tail shark will reach its maximum size in a little over a year. These fish are generally sold as juveniles, measuring around 2-3 inches.

They will grow to their full 6-inch potential throughout the following year. This, of course, depends on whether the fish is getting adequate care and a balanced and nutritious diet.

How to Make Red Tail Sharks Grow Faster?

If you want a faster-growing Red Tail, you should consider lending it a hand along the way.

To optimize your Red Tail’s growth, consider:

The Water Quality and Parameter Stability

Red Tails aren’t exactly messy fish, especially since they’re scavenging bottom-dwellers. They will spend their lives near the substrate, scraping algae off of rocks and consuming various organic matter for their daily dose of nutrients.

Their feeding behavior is one reason why they don’t need as much food from you as other fish.

That doesn’t mean that they don’t need care and maintenance along the way. You should consider partial water changes regularly, although not as often, especially if your Red Tail is housed alone.

Changing 10-15% of the water every 2-3 weeks should suffice, depending on the situation, if the tank is 55 gallons or more.

If the aquarium is only 30 gallons, I recommend a weekly partial water change to remain on the safe side.

The goal is to preserve the Red Tail’s system stability to avoid the formation of ammonia and nitrites.

So long as the water is fresh and water parameters remain stable, your Red Tail will grow into a healthy and energetic fish.

Optimal Diet

This is undoubtedly one of the defining factors influencing the Red Tail’s growth rate and maximum size.

The Red Tail will scrape its food from the hard surfaces decorating its environment, mainly rocks, driftwood, and other aquatic elements. That doesn’t mean that the Red Tail doesn’t require any feeding.

As an omnivorous fish, the Red Tail requires a varied diet but less food overall compared to other tank fish.

You only need to feed the shark every 2 days. Always use sinking food and always make their meals diverse to ensure optimal intake of multiple nutrients.

Red Tails thrive on brine shrimp, bloodworms, daphnia, peas, zucchini, and general fish food.

Just remember not to provide floating foods since the Red Tail won’t swim to the water’s surface to feed. Sinking pellets are ideal, along with the usual live food.

An adequate diet won’t only boost the Red Tail’s growth but will also enhance its natural coloring and improve its immune system.

So, you will have a larger, healthier, and more colorful Red Tail as a result.

The Tank Mates

Red Tails are a bit pretentious when it comes to their tank mates. If you pair them with shy and calm fish, the Red Tail will bully them constantly and even hurt them in the process.

If you add some other bottom-dwellers, your tank will turn into a gladiator ring since Red Tails don’t share their territory with anyone.

If their tank mates are too aggressive, they might bully and even kill and eat your Red Tail. Which is also less than ideal, to say the least.

All these problems have something in common – they will stress your Red Tail. Or straight-up kill them, which at least renders the stress problem irrelevant.

The ideal tank mates for your Red Tail shouldn’t be too shy but shouldn’t be too aggressive either.

The idea is to discourage the Red Tail from bullying or attacking its tank companions, which is why you have 2 options for reliable tank mates. You either go for schooling fish, which use numbers to protect their ranks and intimidate the Red Tail.

Or rely on species like semi-aggressive cichlids, which will keep the Red Tails in check.

These strategies will force the Red Tail to mind its own business and stick to its side of the tank. They will also keep the Red Tail healthy and happy for years to come.

Disease Prevention

This is a major point precisely because it’s so impactful. Red Tails are prone to ich and fin rot, among other freshwater disorders.

Providing them with a clean, safe, and stable environment will help you prevent these health issues in the long run.

Some of the most important strategies to deploy for prevention purposes include:

  • Perform regular tank maintenance and water changes to keep the Red Tail’s system healthy and stable
  • Ensure an optimized diet to provide the Red Tail with necessary nutrients and boost its immune system
  • Prevent fish stress by avoiding aggressive tank mates, foul water conditions, etc.

Aside from that, you should also monitor your Red Tail constantly to make sure you identify any signs of disease early.

This will increase the chance of recovery, which is priceless when knowing that most fish disorders are deadly in advanced stages.

All these measures will allow your Red Tail to grow and achieve its maximum size faster.

They will also keep the shark energetic, healthy, and snappy, just the way you like it.

When do Red Tail Sharks Reach Full Size?

Red Tail Sharks will reach full size by the time they’re 1.5 to 2-years old.

That is unless something doesn’t hinder their growth rate along the way.

Why Has Red Tail Shark Stopped Growing?

If your Red Tail shark doesn’t seem to grow at its normal rate, or at all, consider the following:

  • It has reached its maximum size – Not all Red Tail sharks will reach a 6-inch size. Some will remain in the neighborhood of 4 or 5, for instance. The shark’s genetics plays a pretty important role in this aspect. If its parents didn’t grow too much, to begin with, the offspring are more likely to meet the same fate.
  • Fish stress – Stress will hinder the fish’s growth rate over time. The most common causes of stress include poor water conditions, inadequate diet, incompatible tank mates, untreated parasitic or bacterial infections, etc.
  • Insufficient space – If the tank is too small, your Red Tail will stop growing before reaching its maximum potential. The recommended tank size for a Red Tail is around 30 gallons, but you might need slightly more in some cases. Many aquarists go for a 50-gallon tank for a 6-inch shark.

If your shark doesn’t appear to grow anymore but seems healthy, active, and energetic, it’s probably nothing to worry about.

Provide the fish with the best care and maintenance, and it will resume its normal growth soon.


Red Tails will grow at a moderate rate and will reach their full size typically before reaching their second year of life.

You can speed up their growth considerably by abiding by the strategies I’ve already mentioned.

Make sure your Red Tail is well-fed, healthy, and in peace, and it will grow.

Author Image Fabian
I’m Fabian, aquarium fish breeder and founder of this website. I’ve been keeping fish, since I was a kid. On this blog, I share a lot of information about the aquarium hobby and various fish species that I like. Please leave a comment if you have any question.
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