I have two red tiger oscars they're 3 inches and ive had them for a month. When i got them both they were dense in color, meaning very dark and defined. After a day or so both lightened up tremendously. one was almost all black with red speckles around tail area and a lemon colored breast area now he has patches of two shades of black and two shades of orange. The other was like a road map, black being dominant and orange veins throughout. now he seems to have flip flopped if that makes sense. I took my water to the pet store and they said its good. also they seem to get darker/return to the color they were when purchased as the temp rises in the day. i keep it between 81 F at night to 83 F in the day. i Have them in a 30 gallon now with 50 gallon HOB filter and bubble bar and plan to move them to a 100 gallon with 2 70 gallon HOB filters. Minimal rocks large calico stones with white pebbles and large swim through cave. Just wondering if the color changing is normal(they seem to look different everytime i look at them)
They seem extremely healthy and happy otherwise no ich or bad scales very active and friendly.

oscars do change their color, either when they
are under stress, threatened, or excited but on
normal condition, they do change color as they
grow up. true colors and pigmentation manifest
upon reaching adulthood.

vibrant colors indicate they are very healthy while
dull colors connotes there is problem either in their
water or poor foods combination.

30 gal tank is already very small for the two of them
at this point in time. if you have a bigger tank, they
should have grown for about an inch within that span of
time. i suggest you maintain your temperature at 80 deg,
the ideal temp for oscar.

they will be happier when they get bigger tank. and you will enjoy more seeing them swimming gracefully in a bigger space.

personally i dont trust fishstores to give proper reading when it comes to water quality. many times ive seen a store tell people their water is good and when they test themselves the ammonia or nitrites are high. i would recommend getting yourself a test kit and testing your own water to ensure the readings.

many thngs can stress an oscar and therefore change the colour. water quality, lighting, tankmates ect... as for you tank it already has been adderssed so i wont bother with that however your future ideas on filtration are a little concerning. i personally would not recommend 2 small hob for your 100 gallon tank and instead look towards a canister filter. they are a little more expensive but will provide better filtration in the long run. you should look into a filter that is rated for a tank souble the size you are planning on getting. eheim fluval and rena make good filters and they come in various sizes to meet your needs.

hope this helps

i totally agree with necro....this is one side. the other side is that even if your water is good, they will say it is bad and will sell you all the stuff that are useless. they are just after the sale of their merchandise.

in some instances, they do not test your water at all but will give you result. isn't it amazing???????

Thanks guys, tested water myself today and according to other post im good to go. Previously i had failed to mention that I was having trouble getting feeding schedule. In the beginning when they were adjusting andd wouldnt eat i dropped some guppies in there so they'de eat when they got hungry. Well i read "somewhere" that varied foods could cause color change and they became picky wanting guppies not pellets. now that i have cut out guppies steadily been feeding cichlid gold baby pellets morning and night(about 5 days now) their colors are already darker and defined. For fun i thaw some bloodworms and watch them nab them for 30 minutes or so off the bottom. Developing concerne: sorry new here so lemme know if this is the wrong forum. It pertains to health so..
One oscar is a tad bigger and bullies the other. The weaker has torn fins all over and light abrassion on his sides. Will they work out together?

its possible that they will work out their difference in time but there is no guarentee on it. since they are still small im leaning towards a dominace thing in your tank. if it continues and harm is being done to one of the oscars then you will have to decide on a course of action. however you still have some time so i would keep an eye on things and play it by ear for now.

Thanks, I'll keep an eye out. Is there a benefit to an oscar having a partner?

with proper tank size, it feels good to watch them in tandem
and a chance for breeding later. but solitary healthy oscar is
no difference. it is up to the keeper.

my guy changes color all the time! at first i was worried but now i've seen the change from black to green and back to black again all within a minute or two, usually when i drop in food or swims to a different area of the tank (my tank haas different shades of blue and green as the back drop) it's almost like a chameleon, pretty cool.

actually, they adapt the color or reflection of the environment.
i am not sure how do they do it but i had same experience from
time to time.

I had a pleasant experience at the local big chain pet store. The person checked my water and told me to do the usual water change. Didn't even try to sell me anything. Way cool I must say. But being familiar with what to look for and a bit experience helps out too. Plus the help you get in here is priceless.