How to Prevent Guppies From Eating Their Babies
If you are interested in raising guppies, there are a few things to know that can reduce or even eliminate them eating the babies in the first few weeks after they are born. This goes well beyond providing them with a breeders box, which is often a cramped space and may actually contribute to the mother's eating the young. If instead, you look at the basic needs of guppies in detail, that can help!
Guppies, like all other animals (mammals, birds, reptile, fish etc) need food, water, shelter and space in the right balance to survive and thrive. When these things are not balanced to the needs of the fish, they can be a significant cause of stress. Genetics can also play a role. Let's look at these factors in detail.
Space:
Make sure you have a tank that is large enough for the number and size of guppies that you have and will have in the future. If it is not large enough for future population, then have other tanks ready to transfer the growing or adult guppies to.
One thing I do is to remove the males as they develop and put them in a tank of their own to mature. This leaves us with a maternity tank and a male only tank. Males can also be put in community tanks with fish like Corydoras catfish that won't harm them or nip their tails.
Water:
Since fish live in water, we need to look at the water quality. They are not just drinking it, they are breathing it! What are the chemical levels in the tank? pH, ammonia levels? salt? Are they appropriate for your guppies?
I also consider water temperature as part of water quality. Keeping guppies at the lower end of their temperature range results in a slower metabolism. This means they don't need to eat as much which also means they are less likely to be ravenous if you skip a meal here and there. I keep my tank at room temperature which varies between 19C-23C (67F - 72F) during the year. I still have good baby production at those temperatures.
Shelter:
Shelter for guppies usually means a combination of plants and decorations that provide hiding spots from larger fish. Light levels and substrate (gravel) color can also play a role.
Light Level & Gravel
Keeping gravid guppies and babies in low to medium light levels can help reduce them being eaten. Bright lights silhouette the babies to the adult fish who swim below them. Dim lights help them blend into the shadows of surface plants. If the babies are below the adults, a medium variegated substrate can help them blend in as well. A solid light or dark color makes the babies easy to be seen by the adults.
Top of Water
One common suggestion is to provide dense plant cover for the young. These can be live plants or plastic alternatives. I make sure there are plants on the water surface such as water lettuce, salvinia, duckweed and/or guppy grass. Their roots provide great cover for babies and shelter from bright lights. If I don't happen to have those, then a few species of terrestrial plants like spider plant will grow roots in water. Their leaves above the water can provide some shade from the light.
Middle Water
Plants that are anchored on the bottom but extend to the top provide a protected channel for the babies once they get strong and brave enough to feed on the tank bottom (usually at just a few days old). Examples of these are coontail (hornwort) and Elodea (Anacharis). The more divided their leaves are, the better the cover they provide. Pothos (a terrestrial plant) can grow long roots that provide a link from top to bottom of the tank.
On the Tank Bottom
More plants on the bottom give babies shelter while they feed and to prevent the larger females from eating all their food before the babies get to it. Java moss and willow moss can be anchored on the bottom in a mass.
Plastic plants can be used at all levels. I find finely divided leaves help. One I discovered recently in the floral section at the dollar store is a plastic topiary ball. It has very dense leaves on the outside and a round opening on the inside. This keep the larger fish on the outside and the babies safely inside until they are ready to venture out on their own.
A similar idea is to roll up a piece of plastic craft mesh into a wide tube and zap strap or super glue it together. The tube is placed with the ends up and down in the middle of the tank. The babies swim into the tube to get away from the adults. Use size 7 mesh or lower. The smaller the number, the larger the holes. Size 7 mesh means 7 holes per inch. Size 6 is 6 holes per inch. 5 is 5 holes per inch.
Do make sure there is open swimming water for all sizes of fish. That is how the young learn to avoid predators.
Here is a tour of my guppy tank! Can you see the variety of cover at each level of the tank? Look for all the different plants and the plastic topiary ball.
Food:
Feeding the adults often throughout the day, 3 to 4 times helps to stave off hunger.
Making sure they have some grazing food available at all times can reduce predation as well. Algae left growing on the sides and back of the tank provides extra food that will not spoil. Snail eggs and newly hatched snails are grazed on as well. I recommend ram's horn, wheel snails (tiny version of ram's horn) and bladder snails as their eggs are easy for guppies to peck at and they have softer shells than other species. The snails will eat uneaten food and turn that into more eggs. Since guppies have live young, you don't need to worry about eggs being eaten by the snails.
Using live food like daphnia, white worms, ostracods, springtails, fruit flies, baby brine shrimp and even land mites provides enrichment for the bigger guppies. They focus their energy hunting the live food so won't tend to focus on the babies as much. Live foods also last awhile in the tank so there is less waste and fouling of the water.
Feeding female guppies springtails. I am tapping the container with one hand which slows the process. Just a few days after the first video, there are 50 guppy fry in the tank (along with 9 adult females)!
Stress:
Fish that are wild caught or grown in large ponds or vats will only be accustomed to seeing people approach from the top of the pond or vat. These fish tend to panic when they are transferred into a glass aquarium and see people nearby. At first, the stress of adapting to a new environment can trigger a fish to eat their young. Once they have settled in and learn that people and normal sounds are not a threat, they may stop. Fish who have grown up in aquariums learn from early on that the approach of a person from the side or top of the tank usually means food. They tend not to be as stressed overall.
High levels of environmental stress even in tank-raised fish can certainly trigger them to eat their young. Avoid loud sounds or jarring the tank or major tank redecoration or water changes right around birthing time. Of course there is a normal level of stress they should be able to handle in any home like people approaching with heavy footsteps, loud television etc, but try to avoid any excessive shock to the tank as the vibrations are transmitted to the fish via their lateral lines.
A high density of fish in a small tank can be considered a stress as can poor water quality. As the babies grow, they eat more and poop more. Take that into account for how often you change the water or the size of filter. I prefer to use a sponge filter in baby tanks, or at least use a sponge cover over the intake on a hang on back filter and a low volume.
Genetics:
Added to the above, there may be a genetic factor involved in cannabalism. Choose lines that have a more solid temperament and able to withstand stress. These are less likely to eat baby fish. The fish that zig zag around the tank in panic tend to trigger predatory behavior in other guppies (and community fish). Just like most dogs can calmly watch a rabbit sitting still, when the rabbit starts running, the chase is on! The same applies to big guppies living with little guppies.
I know you are going to ask how do you determine temperament? Ask if they are wild caught, pond or tank raised. Observe the fish for awhile before buying them. See how they react to normal stress like you approaching the tank, or having a net put in the tank. These activities should not panic the fish. They should be curious (will you feed us?), they can be cautious but come back to investigate after a net is swished a few times. You will quickly see the ones who panic. Those tend to be the fish that are really hard to catch. In my observations, those are also the same ones that tend to eat their young.
If you plan on breeding and raising guppies, the above tips should help reduce cannibalism so you can produce more to breed or sell.
These tips can also reduce aggression of fish towards each other as well.
Here is a follow-up blog post on guppies.
