Platy fish not breeding - Why... Help!

Hi my fellow fish keepers!
I have a problem in my Platy tank.
My Platys aren't breeding at all. I have them for about a month now, and still no babies ( I know it takes 4 weeks ) or pregnant females.
When I bought them, all the females were pregnant and after about a weeks time, they gave birth. I gave the babies away about 2 days ago to my friend and they are doing well in his tank. There were about 150+ of them in total.
I have 3 males and 8 females, which is a total of 11 Platy fish. I have kept this ratio in the past and the breeding were perfect.
They are in a 45L tank with plants. I have tested about twice this week and the water quality is perfect.
I feed them Tetra Prima mini granuals and Tetra Pro Energy.
I do a 20% water change once a week and add Prime and Stability to the water.
Please help!
I think I gave all the needed info to help me.
Thanks in advance!
Kind regards, Michael.
Here is pic of tank and fish.

 

Agree with reedfish on the water quality and space. Also look into beter foods to feed. Bbs or white worms, even some bloodworms if you can't find the others.

 

Thanks for the replies @Reedfish and @BoelderBeestie. I have considered a bigger tank because I have one that is a custom made 150L tank but space doesn't allow. I want to begin my own fishroom but I still need to find some space.
I had fed my fish bloodworms once and they did like it but the problem is I can't find a LFS that sells good quality bloodworms. I do feed them live Brineshrimp sometimes if that is ok?
The Nitrates aren't high at all. I clean the filter every 3rd day and add prime to the water...
I will get a LFS that sells good quality Bloodworm and try to put them in a bigger tank after I let the water cycle for a month.

 

I have an 70tank with about 40 to 50 platies mollies swords kribs in they breed like hell i added rams to eat some babies but they not making a dent so tank size isnt an problem.. Water quality and tank scape with feeding could be an issue. You need to keep them well fed but in an way to not affect your water quality. Then scape i have an area full off plastic plants Where the females go hide and drop and the babies hide in the top. With feeding if you dont feed parents well they go for the fry so its an catch 22. Send me an pm and ile forward you some pics .

 

Are you not maybe causing your filters to lose cycle when you clean them so often? Every 3 days is a lot. And if you have to clean it so often then your tank is way under filtered to begin with.

 

+1
This tank i keep the fish for Dithering fish so only time i remember to clean the filter is when its not working. Wc i normally forget about this tank.

 

I dont think I am messing up the cycle. I have been doing this for the past 10 years of keeping fish and haven't lost one fish due to doing this. I will clean the filter once a week and see what will happen. Hopefully this advice you guys are giving me will help.

 

Your temp? Might be a little hot for them to breed. My tanks are all sitting at 31c plus right now, nothing I can do about it but wait for winter. And then moun about it being cold again.

 

My temp is about between 24 - 26°C. I dont put any heaters in my tank in the summer times. It is to hot for heaters. I always use heaters in the winter.
I must agree with you @BoelderBeestie, in the winter I also moun about it. Aai... Life can be hard sometimes for fish keepers. LOL

 

Fish needed minerals in their water to survive, especially platies. As per my experience probably they are not breeding because of lack of sufficient minerals where they can develop their egg. If you want to breed your platies then you need to add minerals back to the water via products such as Equilibrium or Replenish. Not only me if you visit various website Like Fisharoma they also strongly suggest adding the minerals back into your water as soon as possible.I strongly believed that your fish star bredd again after the proper minerals

 

Bred Platties for many years .. Feed alot.. Fatten them up alot.. They probably need more food and add lotsa floating plants for any fry to hide in .