Guppy Tails Being Torn Up Again!

[LicianDragon]

I have a 20 gallon planted community tank. Fish include-
 
3 female guppies
1 male guppy
1 hifin molly
1 red-tiger platy
1 red-tail sand loach
3 julii cory cats
1 hillstream loach
 
I've had issues with fin tearing before that was attributed to an overstocked tank. The tank is fine now but my female guppies are still getting their tails torn up. IT's only the females too. Every other fish in my tank is fine.
The fins are merely torn, they're not red and the fish have no other injuries illnesses. They don't seem overly bothered by it, they're still eating and acting normal (no clamped fins, etc.). Two of the females recently dropped about a dozen fry collectively as well.
 
I'm worried about secondary infections and stress. Any ideas who could be tearing them up? The tank sits on my desk where I'm watching the fish nearly all hours of the day, I've never noticed any aggressive  behavior. Occasionally the red-tail will chase the corys or the molly but its only during feeding and he's never pursued enough to cause injury.
 
Tank stats-
 
Ammonia-0
Nitrites- 0
Nitrates-10ppm
Temp. 74 F

 

[Sophie]

What's the filtration like? Is there any possibility they could get caught in the intake?
 
On an off note, is that your final stocking? It's a bit all over the place, the temperature is a bit off too for a variety of those fish - shoal numbers for the Corydoras are low too

 

[LicianDragon]

What's the filtration like? Is there any possibility they could get caught in the intake?
 
On an off note, is that your final stocking? It's a bit all over the place, the temperature is a bit off too for a variety of those fish - shoal numbers for the Corydoras are low too

Filter is a HOB Aqueon that came with the tank for initial setup. Yes this is final stocking. I had more julii's but a number of them have passed and none of my LFS are carrying them at the time. My temp is actually a little to high concerning the hillstream loach, I need to drop it another 2 degrees I just dont want to stress the fish out by doing it to quickly. The hillstream loach cannot handle anything over that temperature so I have it as high as I can for him.

 

[Sophie]

 

What's the filtration like? Is there any possibility they could get caught in the intake?
 
On an off note, is that your final stocking? It's a bit all over the place, the temperature is a bit off too for a variety of those fish - shoal numbers for the Corydoras are low too

Filter is a HOB Aqueon that came with the tank for initial setup. Yes this is final stocking. I had more julii's but a number of them have passed and none of my LFS are carrying them at the time. My temp is actually a little to high concerning the hillstream loach, I need to drop it another 2 degrees I just dont want to stress the fish out by doing it to quickly. The hillstream loach cannot handle anything over that temperature so I have it as high as I can for him.
 

 
 
Which then makes it too cold for the Corys, Sand Loach, Molly and Guppies? They are already at their minimum temperature now, ideally you want 25/26 not 22/23.
The platy I guess can deal with temperate conditions but I am assuming there isn't a really high turnover rate in the tank adequate for the Hillstream Loach either? He seems to be the odd one out really.
 
I guess there could also be a start on the debate whether Mollies need slightly brackish conditions too

 

[LicianDragon]

 

 


What's the filtration like? Is there any possibility they could get caught in the intake?
 
On an off note, is that your final stocking? It's a bit all over the place, the temperature is a bit off too for a variety of those fish - shoal numbers for the Corydoras are low too

Filter is a HOB Aqueon that came with the tank for initial setup. Yes this is final stocking. I had more julii's but a number of them have passed and none of my LFS are carrying them at the time. My temp is actually a little to high concerning the hillstream loach, I need to drop it another 2 degrees I just dont want to stress the fish out by doing it to quickly. The hillstream loach cannot handle anything over that temperature so I have it as high as I can for him.
 

 
 
Which then makes it too cold for the Corys, Sand Loach, Molly and Guppies? They are already at their minimum temperature now, ideally you want 25/26 not 22/23.
The platy I guess can deal with temperate conditions but I am assuming there isn't a really high turnover rate in the tank adequate for the Hillstream Loach either? He seems to be the odd one out really.
 
I guess there could also be a start on the debate whether Mollies need slightly brackish conditions too

 


The turnover rate is fine and I add salt to my water. Like I said, all my research said the fish were fine with my temperature being 72f.. The hillstream loach has been in the tank for months without any issues. I'm not entirely sure why we're even discussing this as it has nothing to do with my actual concern which is why my female guppies are getting their tails torn up. 
 
Here are just some of my sources for the temperature of all my fish species.->
 
http/www.liveaquaria.com/product/prod_display.cfm?c=830+885+3003&pcatid=3003
http/www.loaches.com/articles/sewellia-lineolata-the-reticulated-hillstream-loach-easy-to-spawn-or-a-whole-lot-of-luck
http/www.fishlore.com/Profiles-Guppy.htm
http/fancyguppy.webs.com/care.htm
http/animal-world.com/encyclo/fresh/catfish/juliicory.php
http/www.fishlore.com/Profiles-Corydoras.htm
http/animal-world.com/encyclo/fresh/HillstreamLoaches/RedTailZebraLoach.php
http/www.seymourfish.com/how-to-care-for-a-molly-fish/
http/www.liveaquaria.com/product/prod_display.cfm?c=830+1103+1069&pcatid=1069
http/www.liveaquaria.com/product/prod_display.cfm?c=830+1103+2944&pcatid=2944