This is the way i veiw breeding nets;
The bad points;
a. they are small are cannot hold any single fish bigger than a small guppy.
b. They can stress the mother fish out if not set up with care.
The good points;
a. if you have say a pregnant molly in a tank with say tiger barbs, the tiger barbs will almost certainly harrass the mother molly no end while she is trying to give birth.
When a livebearer gives birth they release scents in the water and other fish will pick them up and harrass the mother so either
ii. she gives birth to fry in a bad place where they cannot hide and the fry all get gobbled up, or
iii. the mother fish die from stress and the other fish get to munch on her- barbaric but true and almost every fish has the ability to eat its tank mates in the right situation for it.
Breeding nets can be stressful but i do not believe they are anywhere near as stressful for the pregnant fish getting chased around all day long while she trys to give birth.
b. Breeding nets will protect the fry from getting gobbled up; rarely a mother fish will eat some of her own fry but i think this is only help regain her own strength after a very long/difficult birth and is quite rare.
I think there is a time and a place for breeding nets and they can be both good and bad depending on the situation.
There is no doubt they are good for raising fry alone in but it does depend on the situation of the pregnant fish.
Never should they be used to houes more than one fish or be used to try and breed/make fish mate in.
I wouldn't advise using a breeding net in this scenario, but if you need to set one up remember;
a. do not place it directly under the tank lights and if you can't find somwhere for it that isn't directly under them find somthing to shade it.
b. Put a stone in it to help weight it down and put some plant in it to help make the mother fish feel more at home.
c. Place the net where it is good flow/current from the filter.
If you follow these instructions you shouldn't have any problems.
Livebearers can die from giving birth for a variety of reasons i.e they were too young/not strong enough, they had a very big fry load to deliver and couldn't cope, they were being stressed out by tank conditions/other fish for various reasons.
When i started my guppy project i never used breeding nets for the pregnant fish at let them give birth at will where ever they wanted and i would say the survival arte of pregnant fish was no better then breeding net ones.
If a pregnant fish dies in a breeding net, it does not nesarsarily mean it was because the net stressed her out too much- she could have just experienced birthing difficultys which would have occurred in the main tank anyway- there is no way to tell when it comes down to it.
