The thing about keeping fry in a small tank is that they release a growth stunting hormone and if proper water changes aren't made then the fry 's growth will be stunted. Also, even though females have been known to put eggs in nests there is no guarantee that she'll raise the fry. She'll more than likely eat them.
Most likely it will be a case of your actions killing them rather than the father.
You are going to kill your neons.. they are fragile to begin with, putting 6 into a 1g bowl is going to kill them quickly.
You can breed them in the 4g, just set it up to be a proper fry tank. Take out the filter, raise the temp, find another home for the female, etc.
It is doable in that tank, but the filter needs to go - if you were to remove the divider to give the fry more space (saying you gave your female another home), and you turn off that filter (which needs to happen as the filter will push them around and suck them up - kill them quick).. your cycle will crash and kill your fry. You need to get it turned off first, empty the tank, and redo it to make it safe.
"the filter will push them around and suck them up - kill them quick"
The water surface in my tank is completely still, and sponge filters are used to prevent fry being sucked.
@soady: I know people breed differently. I breed in as small as 1g tall/regular tank to 50g long. But you must understand some basic facts.
1. Females WILL NOT care for fry. they will more likely eat them. You MIGHT get away with it IF your set up is densely and fully planted to the top. Leave ALL, male, female and fry . . . this MIGHT work. BUT you need a much bigger tank.
2. The smaller the tank, the bigger the disturbance by air flow of filters. If you're using a 20g, you can use filters for newborns/hatch but a small 4g can only take about 1 bubble per second or more. Otherwise fry will be tossed around and die.
3. Fry are very sensitive. You can't treat them like adults. They are vulnerable towards environmental changes. This will effect their feeding habit.
4. Fry need bigger tanks for their growout. They can only be kept in small containers for a short period because water parameters will quickly crash.
Thanks, Indjo. I am aware that the female will most likely eat the eggs, but it is worth trying with a couple of eggs. The water in my tank couldn't be more still. I might get a 15 gallon bucket for the fry so no worries, I will do it right. :)
Messing around with the nest of eggs with the male can cause him to freak out and eat all the eggs.. messing around with the tank at all with the male and his nest can cause it.. he should not be disturbed at all while nesting/caring for fry. So you trying to scoop a few eggs (which will be hard to see under a leaf, under the cup, under the nest and still be able to scoop) can lead to you killing lots of eggs yourself, and causing the male to kill them. Is it really worth it for an experiment that WILL fail?
15g will be okay for about 10 fry to grow in.. if the father wants to keep 200 alive (since you are using only him to cull).. then what are you going to do with the 190 other fry that need larger space to grow healthy in?
See the flaws in the plan? Breed in the 4g (I breed in 1-2g successfully myself), but make sure the 4g is properly set up. Make sure to have plenty of grow out tanks. And make sure to have jars that you can heat up appropriately.
There may be different techniques to breed in, but they still all have the basic requirements, which you are not meeting with your plan.
There is no way that I will end up with 200 fry on my first spawn, and probably their too. You are exaggerating, jars are easy to get, I already have a bunch, and a 15-20 gallon plastic container will be enough for a decent spawn, heated, floating plants... And I will be able to scoop some eggs with the nest carefully when it's feeding time and he isn't paying attention. It will be only a few, just out of curiosity, because not all bettas act the same. My plan is great.
I could be wrong but I dont think the male eats till the fry are free swimming so trying to distract him with food will not work. Caring for the fry will be stressful enough and add you bothering him trying to get some eggs its just not a good idea.
There is no way that I will end up with 200 fry on my first spawn, and probably their too.
You want to go look at my 300 fry from a virgin that are swimming healthy in one of my fry tanks right now and tell me I am exaggerating? You can EASILY end up with 200+ fry, there are NO rules as to how many eggs are laid.. so yes, there is a good chance you will end up with 200+ fry.
jars are easy to get, I already have a bunch,
Yes they are.. never said it was hard to get them. But you will have to find a way to be able to heat up 100 easily to the proper temp is what I am saying. Don't forget the daily water changes you will be doing on all of them.. so know you will spend hours a day cleaning them out.
and a 15-20 gallon plastic container will be enough for a decent spawn, heated, floating plants...
A 15-20 gallon is good for about 15-25 or so juvies.. depends on whether or not you plan on skimping their care. But it is better to be safer and get another to make sure you have the room.
Find a way to light them up, so your fish won't be stressed living in the dark and your plants have a chance at surviving.. dying plants = dying fish. Make sure it's the right type of light as well for the plants.
And I will be able to scoop some eggs with the nest carefully when it's feeding time and he isn't paying attention.
99.999999% of males don't eat when caring for eggs/fry. Mine don't eat until days after I pulled them. And you will be rushing, and you will be breaking apart the nest doing so.. you just don't understand how the nest works. It is held together by saliva, under a leaf (or cup).. you make a move to the nest the male will immediately start to grab the eggs.. he may or may not eat them at that moment, but he will start grabbing them as quickly as he can to get them from you. WHY are you so insistent on killing these eggs/fry? You don't know.. you won't listen to people who see the nests, who deal with the fry, who deal with the parents, etc.. instead you "want to try something and will do it even though it will kill the babies just because I want to".
It will be only a few, just out of curiosity, because not all bettas act the same. My plan is great.
You can't just grab a few!!!! They are clumped together all around the nest.. he has it set just right to hold the nest together.. you go in there and try to scoop some you break up the nest and then you lost them all.
No they don't, but IT'S THE FEMALE'S INSTINCT TO NOT HELP WITH THE NEST. It's very rare to get anything to go against instinct.
Your plan is ANYTHING BUT great and honestly I hope you try it, see it fails and you lose everything just so you don't keep trying it over and over. This is just plain... ugh... as someone who cares for the well being of animals, I don't want to see them get hurt.
There is nothing wrong with trying new things as long as they are being cared for and not harmed. You are placing them in harm, you are placing your neons into a death trap. How can you not see this?
Myates, Louisville Lady, Indjo and others have all given terrific advise in this thread. I have nothing to add other than these folk are very experienced and any new breeder should heed these wise words.