firstly congratiolations,...second..Dont put the fry back into the 125, if there is some sort of disease or infection chances are you could move it into the 125 with the fry and this could cause bigger issues such as other fish becoming infected also a thing to bear in mind is the larger the tank the more medication you would need to use and the costs can also mount up ...
Being so small the fry may not be able to handle any form of medication you may need to dose and being newborn there immune systems may be weak making them more likely to become susceptible to the possible infection and also making it harder for them to fight off the disease.
As far as the fry go possibly the best thing you can do for them is to make sure that you maintain stable water conditions without doing too large of water changes, although the natural thought for you would of been to do big water changes to help cycle out the possible cause of infection this may not be the best thing to do as changing water usualy means a possible waver of water perimiter's which to young fry could potentially prove more fatal than doing smaller water changes over a longer period of time to flush the cause out of the system.
in the past i have had the same thing happen to me part of the lore when your standing in the lfs is that you think. "hey i pay £1.50 each for the pregnant ones and next week i'll have loads" (in theory saving a bit of cash right ? But no its wrong the problem is that we skip over the sensible fact that is lodged somewhere in the depths of our brain *All living things are more prone to disease, illness and stress when pregnant* this is because whilst pregnant the immune system makes comprimises as to not reject the baby/babies causing an abortion or miscarriage whilst also weakening the immunity for the pregnant one as its priority is to protect the weakest of the two, the weakest being the younger ...
....*edit*....
*After the parent has given birth she may be stressed, hungry and very weak but also her immune system may take a while to return to functioning correctly it is usually wise to leave her seperated from not only the main tank but also from the fry as it is commonly known for a new mother to consume her young due to hunger and mistaken identity for food, 24 hours is usually enough time for the female to regain her strengths and be ready to be re- introduced to the main tank though this seperation can be prolonged if you do not feel she is ready.*
yes that is a bit of a long read and if you managed to make it to the end you did well
I am not a profesional on this matter but that novel i just wrote may help to give you somewhat of a more complex understanding of at least some possible useless information i have been storing in a forgotten corner of my mind,
Any other readers can feel free to correct me if any of that seems wrong or if i may of missed something?
also, sorry but i have not had much practice as a writer in a long time so there may be numerous gramatical and spelling errors need i mention the posibility of incorrectly utilised words but thanks for taking the time to read my over excessive technical explainations
good luck and let us know how it goes
