How do we increase grass level?

We have the SF feeder and water the grass regularly. But the grass level keeps dropping - we have three animals on each feeder. This morning the grass level dropped to zero and our animals are hungry now. What increases the grass level? Thanks.

I must admit I stopped using the grass feeders for a while as I found they only seemed to support one maybe two animals. They should show 'overgrazing' if there are to many animals using them, but they didn't seem to do that. I'm just testing out some modified ones on my farm on Aquino (Talam farm) and you are more than welcome to visit and take a copy of those ones. They should support 3-4 animals per feeder and do seem to show overgrazing if to many animals are trying to use them.

Thanks Cnayl. That certainly answers the question. What grid is your farm on? I'll be happy to visit.

My farm is on the Quintonia grid

worlds.quintonia.net:8002:Aquino

Is the Aquino grid down? I've tried teleporting there a couple of times without success. I was looking for the modified grass feeders you mentioned (last year). 

Sorry, yes it went down but is now back up again