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breeding tetras


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If you've got a handful of serpae or silvertip tetras odds are they're already breeding on a regular basis. They're egg-scatterers and have likely carpeted your tank with eggs on multiple occasions already, but they also are egg eaters and tend to eat them almost as quickly as they're laid. Feeding the parents live food or good quality frozen food will often encourage more spawning. If you're serious about saving the eggs and raising fry, you'll want a way to protect the eggs as they fall to limit predation. Spawning mops, mats of java moss, even mats of hair algae can all work. Old school breeders would carpet the bottom of the tank with marbles a couple of inches deep so the eggs would roll off and down between the marbles where the fish couldn't get to them as easily. For bigger tetras like serpae tetras an egg crate plastic light diffuser can be used to let the eggs fall through the eggcrate to the lower part of the tank while keeping the parents trapped above it. The water level above whatever egg protecting option you choose is important also. If the tetras breed high enough up in the water column, they can circle around and eat the eggs as they slowly fall. If there's only an couple of inches of water above the egg protection stuff it gives them less opportunity to gulp down the eggs as they fall.

A female who's ready to spawn will typically look a bit chunkier than normal due to the eggs inside her. Males will color up a bit. Once the eggs have been laid, it's time to move the parents (and any other fish in the tank) out. The fry will hatch out in a few days, feed on their yolk sac for a couple of days and then need food. Lots of food. A hundred or more eggs can be laid per spawn, so there will be lots of hungry little mouths to feed.

Pretty much all tetras spawn a lot. And I mean a lot. Over the course of a year a Momma tetra likely lays a thousand or more eggs. The reason we'll not all knee deep in tetras is because they and other fish in the tank then eat the eggs. The fry survival rate in a tank with adult tetras and other fish may be 0.001%. An egg has to be very lucky to survive to the hatching point. The fry then has to be insanely lucky to survive until it's big enough not to be eaten. If you look at a well maintained tank with a school of neon or cardinal tetras in it, you'll notice a few chunkier females. If you watch them closely for a while you'll see them spawn. You'll also see a feeding frenzy emerge as the eggs drop and the other fish in the tank, along with parents, gulp down the eggs. You'll find lots of tanks with big schools of tetras, but in most of those tanks you never find any young fry that have survived. The eggs get eaten, the fry get eaten and the survival rate is very, very low.

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@gardenman has given, what I think is an awesome answer here! I'd like to set up a major tetra breeding tank down the road. I think that we will probably set up a 40 gal tank with a thick, thick mass of java moss -- maybe 4-5 inches thick -- all over the bottom. As described above, the goal is to allow some eggs to fall through the moss and reach a depth of safety, hatch and have a fighting chance of survival down low in the mysterious depth. Another thing I think we'd try is "tinting" the water. Adding tannins calms many Amazon tetras. Again, as was already mentioned, live food is a major, major key. Live brine shrimp and live Daphnia are important. Also, using rain water (or ground water from a sump) as part of water changes can be a helpful trigger. 

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14 minutes ago, Maggie said:

@gardenmanthat sounds just like danios and rasboras, too! My danios go hunting specifically for eggs and fry  every day - head down and eyes just a couple millimeters from the substrate, and glass-skimming top to bottom. 

Yeah, most people don't realize how many eggs get laid in a typical tank only to get eaten by the fish. Most of the common egg scatterers breed very frequently, but few fry ever survive. Setting up a tank for the eggs to survive in is the first big challenge. There are lots of ways to approach that. The stainless steel mesh used by MickS77 is perfect for smaller fish. Egg crate works well for larger fish, Plants and breeding mops help, but I've seen the adults burrow into plants and mops for the eggs so you still lose some. Marbles are the old-school technique, but the problem with marbles is some fry will die and some food will fall between the marbles and spoil. You can't really take out the marbles without hurting fry and eggs so water quality becomes an issue. It's a great way to protect the eggs, but makes a lot more work for the fish keeper in the long run as maintaining the water quality becomes a headache.

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