Well I have alot of thought about this very thing over the years.
In the wild, rays are not able to eat everyday, or not as much as we feed them. Fish are also the same way.
I feed only one time a day now. Every evening. Then do not feed on Sundays.
Sundays I do water changes on the ray tanks.
When I first got rays, I read were feeding twice a day was best. So I did. But also had to do three water changes a week.
Now of course since then, my filtration has been stepped up and is better than what filtration was out years ago..
So about a year ago, I decided to cut back and see what happened.
I did an exp on the rays so to speak.
I had two tanks with Motoro rays
So I fed one like everyone said to do. Twice a day.
Fed the other tank, one time a day. (this tank got half the food as the twice a day tank being I only fed it one time a day) didnt cut back on portions, just amout of feedings.
I did this for 3 months.
I had to do less water changes on the once a day tank.
Rays still were active and healthy. Didnt see any change and no weight loss. Tail base still stayed nice and fat.
So that is when I decided to cut all my tanks back to one time a day.
And I have never fed on Sundays. This is my water change day now for all my ray tanks. This to me, like others have said it was a day of rest for the tank itself...
Time for water to catch up and mix in..
I saw no point in feeding that day and also doing a water change.. To me, not alot of point to add in nice fresh water, then mess it up again with food waste.
Of course everyone does their own thing. This is mine and works for me.
Has cut my food cost by half...(as the rays get bigger, food amount does go up)
water changes have to be less now.. (larger filtration has helped with that as well, Fx5 filters) and i stay on the testing of my water. Always looks good.
Do not see a change in the health of the rays..Active, healthy, growing and doing good..
thats my plan and sticking to it..
