O seems to be more aggressive at the moment towards one of our silver dollars, we think we have a female & a couple of males, the largest SD that we think is female got very fat looking and then I noticed recently some small spry fish on top of tank. Yes O did polish them all off! But for some reason he seems to have taken to biting her - over the last few days - she has quite a big bite mark on her side, it hasn't broken the scales to flesh, but you can see the marks on the bottom of the bite from his teeth.... I caught him do this a week ago, when they were both in the same space - they seem to like the same part of the tank & she had to jump to get out of her way, because what he did was pushed her into the glass & then had a bite. she healed up from last week, but now I see another bite mark, it only appears to be her that he is having a go at. (there are 3 SD's) I was reading that if you change the tank abit O might stop being aggressive - is this worth trying? I dont think he's going to kill her, but its not nice to see!
appreciate some thoughts .....

rearranging the decorations in the tank may change the Oscars attitude, but it's no guarantee.
I see quite a bit of aggression in my tank towards the SD's , but mostly the SD's are too fast to get hurt by my Oscars.
But there's scales flying around the tank from time to time when my O's timing is right...
But more damage is done between the Silver Dollars themselves.

How big is your tank?

If the tank is big enough for some more fish, I'd say get some more female SD's to get them schooling a bit more and have the Oscar's aggression divided by more fish to chase.
On the other hand, if they're spawning they must feel at home.
I never saw any young SD's in my tank, allthough there's enough love to go round between the 6 of them.

As noddy says rearranging the tank may help but some oscars are downright aggressive. Just keep an eye on things and if the aggression gets too bad then think about rehoming. If the O makes a fish miserable (hding all the time or getting badly injured) then its time to rehome.

thanks for that, I dont think we have room for 2 more? the tank is 240litres, we got 3 to start with as that was all the shop had in a size that wasn't too small, and they were in their own little group in the tank so we thought they would be OK, Oscar doesn't do it all the time, it just seems to be when she goes to one particular part of the tank and gets in his way, he nails her against the glass before she can get out of his way! And you are right the SD's play chase around the tank quite alot and that does send scales flying ...