Can Silver Dollars be kept with Oscars?

Question
QUESTION: Hello, I have a 150 gallon livestock tank that I've used as an indoor pond for over a year now.  When my other fish passed on, I decided to keep 4 Oscar fish in there instead.  They are various sizes from 2" to 4" and are gluttons (I try and watch about that!).  

I 'saved' a Silver Dollar fish that was going to be put down because he had one eye and wasn't selling, poor thing.  Anyway it is doing great in my 29 gallon tank, then I read they need others of their own kind so I got 3 more.  Now I know they need WAY bigger than a 29 gallon, it's just the biggest tank I have to put them in as they are very small right now.

They range from nickel to a quarter sized.  Could I put them in the 150 gallon with the juvenile oscars?  I have a big cannister filter on it and do my water changes/filter changes.  I'm told they make good co-habitants but you have to watch how fast the oscars grow compared to the silver dollars.  Will oscars eat them?

The only other tank I have that's large is my 75 gallon but I have African Cichlids in there ranging in size from 1.5" to 3" at most.  They grow very slowly it seems.

What's your opinion?  I'd like to keep the Silver Dollars as I find them so peaceful and gentle looking.  They don't bother the 2 Angelfish they're with in the 29 gallon now, but I know this setup can't last forever.

Thank you so much!
Paula

ANSWER: Hello Paula:

In the past I have also kept Silver Dollars with Oscars and they have done very well together.  While these fish can work great together I would personally worry about the size difference that exists between your fish.  

Considering that you have a 4 inch Oscar I would worry about the smaller Silver Dollars (nickel/Quarter sized) potentially getting abused or eaten.  In addition you are correct that the Oscars will grow at a faster rate so this size difference will increase.  Ideally the Silver Dollars should initially be similar sized, or larger, than the Oscars.

I would also be concerned about moving them to the African Cichlid tank due to the potential of aggression (depending on species) and the possibly higher PH level of that tank.

I cannot say for certain that moving the Silver Dollars to the Oscar tank will not work, but personally I would not try it given the size difference.   I believe that there is a good chance that you could lose some of them.

If I can be of any further assistance just let me know,

-Brian.



---------- FOLLOW-UP ----------

QUESTION: Thank you Brian.  How long can I keep the 4 Silver Dollars in the 29 gallon tank?

Thanks
Paula

Answer
Hello Paula:

Full grown Common Silver Dollars probably need at least a 55 or 75 gallon to comfortably house a small group.  While the growth rate is variable, I would guess that most Common Silver Dollars can reach about 4 or 5 inches within a year with growth slowing after that.  While not ideal, my guess is that you might be able to get by for a year or so - just keep an eye open for any damage or signs of stress.

-Brian.