Raising Healthy Fry: Everything You Need To Know

So you are stuck with a bunch of fry in your aquarium and you aren’t exactly sure what to do with them?

Or maybe you are getting into breeding and want to know all of the ins-and-outs of raising healthy fry?

Whatever the case may be, successfully raising healthy fry is not always an easy task. There’s more to it than simply leaving them be and hoping for the best. 

The water conditions must be almost perfect, you need to feed them the right foods and you must know how to protect them from other fish in your aquarium. 

I’ve written this article to breakdown everything you need to know from the very beginning including: 

• The different types of fish fry and how to identify them
• How to setup the perfect environment for your fry to thrive 
• What you should be feeding your fry
• What to do with unwanted fry

And much more. 

Let’s start by breaking down the many ways in which fish can spawn. It’s important to know what kind of fish fry you are dealing with, so you can adjust your care accordingly. 

Don’t worry, I will try to make it as fun as possible…

There are several different ways in which fish can spawn their young. Knowing which type of spawn you are dealing with can help you tailor your care to their specific requirements. 

Let’s take a look at each type, with some examples of fish that spawn that way:

Bubble Nest

Also known as foam nests, a bubble nest is exactly what it says on the tin – It’s a collection of bubbles, (mixed with an oral secretion – a fancy term for saliva)  that float on the surface of the water. 

The bubble nests are created to protect and incubate the eggs until they hatch. The fish will more than likely be on guard the entire time, to keep the nest safe from other fish. (Usually the male)

Fish that create bubble nests are known as aphrophils and include fish such as:

• Betta Fish
• Gouramis
• Eels

It’s always a good idea to have some floating plants, or at least some corners of your aquarium that are guarded by plants to facilitate your fish’s efforts to protect the eggs.

Mouth Brooders

Mouth Brooding fish are fish that incubate and protect their fry (and even fertilise their eggs) while holding them in their mouth. 

The female will typically hatch her eggs, then collect them in her mouth (the technical term: Buccal Cavity) where the male will spray sperm directly onto the eggs to fertilize them. 

Examples of mouth brooding fish include:

• Malawi Cichlid
• Tanganyika Cichlid
• Arowana
• Cardinal Fish 
• Snakehead

Livebearers

The most common fish found in home aquariums tend to be livebearers. 

Livebearers are fish that carry their eggs inside them, and give birth to live, free-swimming fry. 

Livebearers are often chosen by breeders because caring for live fry is easier than caring for eggs and larvae. 

Their size advantage and ability to swim freely increases their chance of surviving (although being eaten by bigger fish will always remain a threat unless you keep them seperate – more on that later) 

Common examples of Livebearer fish include:

• Guppies
• Mollies
• Platies
• Swordfish

Egg Buriers, Depositors and Scatterers

In almost all cases, if a fish is neither a livebearer or a mouth brooder, they will have some way of releasing their eggs into your aquarium.

Some will scatter their eggs across the entire aquarium or pond (Koi carp for example), some will gently deposit their eggs onto a plant or rock (Angelfish and Rasboras), and others will bury their eggs in the substrate (Killifish).

The way in which your fish deal with releasing their eggs will be obvious to you if you observe their behavior. 

Be sure to check inside ornaments, plant pots, and around your plants regularly for signs of eggs.

For egg buriers, the burial site will typically be marked by an unusual shape within your substrate. 

Again, it’s pretty obvious when you see it. If a certain fish is constantly surrounding an area of your aquarium where these burial sites are, chances are there are eggs inside that they are trying to protect. 

There aren’t many egg burying fish that are found in home aquariums. The most common is the Killifish. 

In this section, I will cover the basics of caring for your fry, regardless of the species of fish and the kind of spawn they produce. 

Because fish fry are so fragile and delicate, you need to know exactly how to care for them to make sure they safely reach adulthood and are as healthy as possible.

The parents can only do so much. Your aquarium is an ecosystem with a lot going on, so you have to be there to assist the parents in raising the juvenile fish. 

Let’s start with discussing housing: 

You typically have three main options when it comes to housing your fry. 

You can either: 

Keep everything all in the same tank.

This is a more natural process, as everything will play out as it would in the wild. The only difference is, you will be feeding them. The upside to leaving things as they are is that it’s less effort on your behalf.

You simply let nature run its course and see how the cards play out. The downside is that you will lose considerably more fry if you were to leave them in the same tank as other fish. You also need to consider environmental dangers such as the filter, water flow, and sharp edges.

Keep them in the same tank, but separated by a tank divider.

By keeping the fry in the same aquarium, you have the added benefit of keeping the water and everything consistent. Moving fry to and from different bodies of water can lead to unwanted deaths due to the subtle changes in water chemistry that aren’t dangerous to adult fish, but are to fry and juveniles.

The divider can keep the fish safe from other fish, and you can decide what section of the aquarium you keep them in, away from any environmental hazards.

The third (and in my opinion the best) option is to install a breeder box.

If you haven’t seen a breeder box before, they simply sit on the rim of your aquarium, providing an enclosed, safe space for your fry to develop, while still being sat in the same aquarium.

You could quite as easily set up a breeding tank to raise the fry, but that comes at extra cost and increased risk. However, if you’re serious about breeding fish, setting up a dedicated tank is something to consider. 

Changes in water temperature, pH, hardiness and ammonia levels are important things to track in every aquarium, regardless of the life inside it. 

When it comes to raising fry, however, the risks of losing them is greatly increased if the water parameters are not optimal and consistent, and if the physical environment is not correctly contained. 

Fish fry have immature immune systems, meaning they are not yet equipped to deal with the hardship of aquatic life. 

Fry are much more susceptible to all kinds of disease (Fungal, bacterial, viral and parasitic). 

Poorly filtered water and constantly fluctuating water parameters are surefire ways to reduce the survival rate of your fry, so it’s important to make sure your water is as stable as possible before even considering breeding.

Here are a few things to consider when raising fry in your home aquarium: 

Test Your Water Frequently

Knowing is the first step to controlling.

You can’t optimize your water if you don’t test it regularly. Be sure to test your water at least weekly to note any changes in water chemistry. Ammonia levels must be zero.

Do frequent water changes.

Water changes are the best way to control the ammonia levels in your aquarium. However, too big of a water change can throw off the parameters for a short while.

That might not be an issue with your adult fish, but for fry, any changes can be fatal.

I recommend changing your water by 10% every 2 or 3 days. For smaller tanks, more frequently will serve you better.

Maintain Consistent Temperature

The fry will be fine in the water temperature that its specific species prefers, whatever that may be. It’s not necessarily the temperature itself that’s the issue, it’s the fluctuations.

Simply check what the optimal temperature is for the specific fish in question and use a thermometer to make sure it stays stable.

Calcium is super important.

A lot of fish will not absorb calcium from their food, but rather from the water itself.

A good rule of thumb for calcium levels is around 20 parts per million. You can test water calcium levels using a simple calcium test kit. Too much calcium can lead to issues in your aquarium, so testing for it regularly is a good idea anyway.

There are also several environmental hazards that you will need to be wary of. Here are a few pointers to keep in mind: 

Good Filtration Is Key (But Not Too Fast)

Good filtration is obviously a crucial part of maintaining stable water conditions, but not all filters are the same. The amount of flow (water movement) can be an issue for young fry if it’s too high.

Also, the filter intake can easily swallow up your fry if it has an open-ended source. Sponge filters are the perfect filter for aquariums with fry. They keep the water clean while eliminating the risk of your fry being sucked into their demise. If you don’t have a sponge filter, simply cover the intake with a piece of sponge.

Watch Out For Other Fish

Fish aren’t fussy eaters. If it’s small enough to go in their mouth, they will give it a try. Fry and juvenile fish are not even safe around their own parents.

It’s completely normal for fish to eat their own fry. That’s why breeding boxes are so useful. They keep the fry in the same aquarium, but outside of harm’s way.

Provide Plenty Of Plants and Hiding Spaces

But nothing too sharp. Lot’s of plants will not only help to keep the water oxygenated and clean but will also provide shelter for both the courting couple and the juveniles they rear.

Feeding your fry (baby fish is a much cuter name, right?) needs a few extra considerations than when feeding adult fish. 

How you feed your fry depends on the stage of their development. 

For fish that spawn larvae, a yolk sac is typically attached to provide nutrition until the eggs fully hatch. In that case, you don’t need to feed them anything, just keep them safe.

After the eggs hatch (or after a livebearer has given birth to live fish), you need to be super consistent and strict with your feeding. 

Fry have fast metabolisms and don’t have the ability to survive without a consistent supply of food. Feeding them several times per day will be required at the start. 

Keeping your fry in a breeding box makes it far easier to feed them consistently without the mess and without the hassle from other tank mates.

In The earliest stages, I’d recommend sticking to powdered and liquid foods. 

Liquid foods such as Liquifry are specifically designed to feed egg-laying fish from the moment they hatch. 

The microorganisms in the liquid will not only feed the fry directly but will also encourage the growth of infusoria in your aquarium, for the fry and other fish to eat when they please. Which brings me to the next recommendation…

Infusoria

Infusoria is a broad term given to all of the microscopic creatures that develop naturally in your aquarium. While you generally can’t see them with the naked eye, they pack a nutritional punch.

If you keep plants in your aquarium, chances are you are already harboring infusoria in your water – simply in smaller numbers. Not enough to nutritionally support your newly hatched fry. 

Choosing a liquid food such as Liquifry is the perfect way to add infusoria cultures to your aquarium. Alternatively, you can learn to culture your own (it’s way easier than you think).

A lot of commercial liquid foods will also contain egg yolk, which can also be fed directly to the fry.

Egg Yolk

Egg yolk, thanks to its high protein content, has been used by Fishkeepers for decades. Long before commercial fry foods became available. 

But just because it’s an old habit, does that necessarily make it a good one? 

It depends. Egg yolk is incredibly nutritious and high in protein, but it can be a mess trying to feed it to your fry. 

You have two options: 

Simply use a dropper to place the egg yolk directly in front of the fry. We use egg yolk because it’s particles are small enough for the fish to consume and again, it’s also high in protein, which is necessary to help them grow into healthy, strong adult fish. 

Alternatively (for larger fry)  you can hard boil your egg yolks and wrap them in a fine nylon sheet, letting them float in the water for your fry (and fish) to nibble at whenever they need a quick protein boost.

Quick Tip: Don’t leave the egg yolk in the aquarium for more than a day at a time. Let the fish feed for a while, then remove it. You don’t want the egg yolk spoiling and spiking your water. 

Green Water 

Another ideal fry food that is easy to make is green water. 

What is it you ask? It’s simply water that has been taken over by algae, turning it green. 

Algae will naturally develop in an aquarium, but again it’s not enough to sustain a batch of newly born fry. Adding extra algae is a quick, easy and cheap way to provide some plant nutrition to your fry and fish. 

It’s perfect for herbivorous fish who require plant material in order to develop a strong immune system. 

Making your own green water is simple: 

• Scrape any algae from your tank walls, rocks or pants in your aquarium. 
• Place the alga scraps in a jar of water and place it in direct sunlight. 
• Every day, stir the water and wait about a week. 
• At the end of the week you will have a bright green liquid that is packed full of nutritious algae.

Please note: Don’t simply pour the entire jar of green water into your aquarium – start by adding small amounts at a time.

Replacing the lost water with new, fresh water will help to keep your supply of greenwater consistent. Your own little nutrition production line. 

Brine Shrimp

Aside from the liquid food that I recommended before (for newly hatched fry), nothing will encourage the growth of your fry as quickly as brine shrimp. 

These tiny, nutritious shrimp are not only the perfect snack due to their protein content, they are also a live food, allowing your fry to train their natural hunting instincts. 

Most fry, even the fussiest of eaters will enjoy a feast of brine shrimp. Pair it with a generous glog of green water, and your fish will be dining like kings. 

Brine shrimp are cheap to buy, but also easy to culture yourself. We have an in-depth guide on the process here. 

Recommended Brine Shrimp:

I’ve used a lot of different brine shrimp products in my time, but the best option I have found is the freeze-dried shrimps from Omega One.

For feeding your fry, simply grind up a few in your fingertips and sprinkle into the water. Freeze-dried shrimp store for months and still hold the same nutritional profile, making them ideal for not only fry but any other fish in your aquarium.

Flake Foods

Flake foods, while messy and damaging to your water quality (if overfed and left to rot), are ideal for both fry and older, juvenile fish because of their nutritional profile. 

Most commercial flake foods are simply a mash-up of your fish’s favorite foods, pressed into an easy to digest flake. 

The flakes on their own will be too big for your fry, but by grinding them into a powder, you can provide your fry with a nutritionally complete meal. This is probably the easiest and simplest way to feed your fry, so it’s ideal for the lazier aquarist (like myself). 

One thing to note; with flake food, not all are created equally. Lot’s of cheap, non-brand flakes are mass produced and full-to-the-brim of fillers and other nasties that your fish simply don’t need. 

Choosing a high-quality fish flake from a trusted brand is a good way to make sure your fish are eating nothing but real food, not chemically altered garbage. (like these spirulina-based flakes from Ocean Nutrition)

There are several reasons why you would potentially need to get rid of your fry, and there are several ways you can go about this. 

If your fish have given birth without you knowing and you have no space, or desire to raise a bunch of fry, then you have a few main options:

• Give them to your local fish store

• Give them to a friend, or another local fishkeeper. 
  
• Offer them to the fish in your aquarium as feeder fish*

Note*: Not everyone is comfortable with the idea of using your fry as feeder fish, and that’s fine. You don’t have to do that if you don’t want to. It’s worth noting, however, that fish will often eat their young. It’s simply a part of the natural process for fish, so by offering your unwanted fry as feeder fish, you aren’t doing anything wrong. 

You can always find other local fishkeepers on Facebook groups or local forums who will gladly take your unwanted fry from you. Whether they raise them to adults or offer them as feeder fish, the responsibility is out of your hands. 

How Can I Cull My Fry?

If in the event that you can’t find someone to take your fry and you don’t want to offer them as feeder fish, the only other option is to cull them.

While I wouldn’t recommend culling as your first option (it should be the very last option), it’s sometimes necessary.

Some fry will have obvious defects that will only get worse as they grow. Fish with defects are far less likely to survive in your aquarium if they make it to adulthood, and in most cases, will be bullied and potentially killed by other fish. 

You also run the risk of the defective fish breeding, passing on their defective genes to their fry, further perpetuating the problem.

Culling defective fry as early as possible (as soon as you notice any defects) is the most humane way to deal with them. 

If you don’t want to offer the fry to your other fish as feeder fish, your next best option is to use clove oil. A few drops in a jar of water with the fry will anesthetize and kill the fry as quickly and as painlessly as possible. 

In Conclusion

This was a long one, but it’s important information to have handy in your brain. 

Whether you’re currently dealing with a batch of fry, expecting a batch of fry, or are purposefully breeding your fish as a hobby, knowing how to raise them successfully will make your life and the life of your fry much simpler and happier. 

If you need a roundup of the equipment I would recommend, here are what I would consider the essentials: 

• Breeder box
• Liquid Food or Brine Shrimp
• Clove Oil 

I would love to hear your thoughts on this topic. 

What has been your experience with raising healthy fry? What are your thoughts on using fry as feeder fish? Do you have any success stories of successfully raising fry? 

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