How Long Before Fry Are Safe In The Tank?

[DWhitehead]

We've had a birth spurt at my house, and I was wondering how long it takes before the baby fish become big enough to not elicit hungry looks from the other community dwellers. I don't have an extra tank and don't need a zillion children in my already crowded aquarium, so I've been letting nature take its course. On the other hand, I have a lot of floating foliage so the fry have some hope of survival. Some mollies were born about a week ago; when I noticed them I could count about six and now there are two. I had another birth on Saturday; I believe that they are guppies because they are super small; the original 10 (at least) is now five as of last night. I even recently discovered a diamond tetra, just a bit bigger than my baby mollies, hiding in the plants. Now that was a surprise!

I have four adult mollies, two adult guppies, four diamond tetras, one congo tetra. Could someone suggest how long it will take before the baby fish are relatively safe? I've been feeding a bit more often lately with more small water changes in order to keep the fish a bit more sated and also because I've read here that young fish need more frequent feeding -- normally I feed them sparingly.

 

[theotheragentm]

It's based on size, not time. Some of the fry will never get eaten, even when they are small enough to fit in the mouth of adults. I don't know why this is, but I've seen it. They swim around like the boss of the tank, but to be safe, go by size. When they are large enough not to fit into adult mouths, you will be okay.

 

[DWhitehead]

Thanks. I was looking for a general estimate of the time. Also, length or width? The molly fry are longer than the adult molly mouths are wide, but I could imagine an adult molly sucking one of the children down like a strand of spaghetti. Yum, spaghetti sushi.

 

[theotheragentm]

4-6 weeks is an approximate estimate depending on growth.

 

[SnBMeg]

Roughly 2 weeks, in my experience. It depends on a lot of factors (and I'm not sure on the size of the tetras), but I've found that usually by then I can move them in safely. I've never (yet) had to wait more than a month to make the move.

Think about if you were a hungry fish, and you saw a delicious little fry. Would the fry be easy to gulp down? Or would it more likely get stuck if you tried? The fry don't need to be wider than the adults' mouths, just large enough that they look too large to comfortably fit. You might still lose fry at this point, but the chances are fairly low.

 

[lee j]

when i first got my fish i noticed a small grouping of mollie fry under the rocks one day and I decided not to fish them out and seperate them because ofthe stess, I only counted 10 and theres 8in my tank today, almots full adult size, - altho there was probaby more and they got eaten!

 

[theotheragentm]

Roughly 2 weeks, in my experience. It depends on a lot of factors (and I'm not sure on the size of the tetras), but I've found that usually by then I can move them in safely. I've never (yet) had to wait more than a month to make the move.

Think about if you were a hungry fish, and you saw a delicious little fry. Would the fry be easy to gulp down? Or would it more likely get stuck if you tried? The fry don't need to be wider than the adults' mouths, just large enough that they look too large to comfortably fit. You might still lose fry at this point, but the chances are fairly low.

I've seen adult fish suck in fry that looked too large. Fish are not discriminate. They go on instinct. They'll try to eat anything floating by if it looks like food. You've all seen them eat their own waste. an overestimate on size is the only safe way to ensure the fry will not be eaten, because not only will they be larger, but they will also be able to swim away.

 

[-germ-]

Agree with theotheragent i've seen my Betta female suck in pea halves in one go that you wouldn't think could fit and good sized pieces of (long story) prawn...

 

[SnBMeg]

Roughly 2 weeks, in my experience. It depends on a lot of factors (and I'm not sure on the size of the tetras), but I've found that usually by then I can move them in safely. I've never (yet) had to wait more than a month to make the move.

Think about if you were a hungry fish, and you saw a delicious little fry. Would the fry be easy to gulp down? Or would it more likely get stuck if you tried? The fry don't need to be wider than the adults' mouths, just large enough that they look too large to comfortably fit. You might still lose fry at this point, but the chances are fairly low.

I've seen adult fish suck in fry that looked too large. Fish are not discriminate. They go on instinct. They'll try to eat anything floating by if it looks like food. You've all seen them eat their own waste. an overestimate on size is the only safe way to ensure the fry will not be eaten, because not only will they be larger, but they will also be able to swim away.

That's why I said "You might still lose fry at this point." The OP said

how long it will take before the baby fish are relatively safe?

so that's what I responded to.

You can't estimate based on the size of the mouth when the fish is just swimming around, because most fish can and will open their mouths quite wide in order to eat. Instead, see how large it is when the fish is trying to wolf down a large piece of regular food--give it something larger than the fry and see how it handles that. If the fry are bigger than what the other fish can normally eat, they'll probably be okay, but until the fry have grown significantly, there are no guarantees that they'll survive in an adult or community tank.

If you want to keep all of your fry, I wouldn't put them in with other fish until they're close to adult size, or at least as large as the other fish's heads. That's what grow-out tanks are for.