Why is my oscar not growing..

  • We are currently upgrading MFK. thanks! -neo

joshua752

Plecostomus
MFK Member
Dec 7, 2013
296
72
61
United States
This happened the last time I had an Oscar and it stopped growing at about 8.5 inches and its frustrating me I just want a giant bruiser finally. I bought him at 1 inch long and i got him almost 7 months ago.. He is only 5.5 inches at this point and isn't growing fast anymore at all.. i feed him and the others a blend of hikari bio gold and omega one super color pellets as a staple.. with nightcrawlers, krill, mealworms, crickets, bloodworms, and peas to supplement Did I get another runt of the litter or what's the deal... he lives in a 125 gallon tank with a cascade 1500 filter and a tidal 110 filter adding another 110 next month. But anyways the tank is kept at 76 degrees his tank mates are a firemouth, featherfin syno and a jack dempsey. I perform a 50 percent and a 25 percent water change weekly. The tank parameters are excellent 0 ammonia 0 nitrite never got above 35 ppm nitrate. I clean the canister once every 2 months the tidal ever 2.5 weeks. So why in the heck is this fish not growing.
 
  • Like
Reactions: tlindsey
This happened the last time I had an Oscar and it stopped growing at about 8.5 inches and its frustrating me I just want a giant bruiser finally. I bought him at 1 inch long and i got him almost 7 months ago.. He is only 5.5 inches at this point and isn't growing fast anymore at all.. i feed him and the others a blend of hikari bio gold and omega one super color pellets as a staple.. with nightcrawlers, krill, mealworms, crickets, bloodworms, and peas to supplement Did I get another runt of the litter or what's the deal... he lives in a 125 gallon tank with a cascade 1500 filter and a tidal 110 filter adding another 110 next month. But anyways the tank is kept at 76 degrees his tank mates are a firemouth, featherfin syno and a jack dempsey. I perform a 50 percent and a 25 percent water change weekly. The tank parameters are excellent 0 ammonia 0 nitrite never got above 35 ppm nitrate. I clean the canister once every 2 months the tidal ever 2.5 weeks. So why in the heck is this fish not growing.

It could be various factors for example genetics, nitrate or total dissolved minerals may have been higher than you thought. Also most Oscars are farmed bred. I would also suggest a sump over a canister filter.
 
Fair enough. I just really didn't want another runt oscar 2 times in a row it feels like its happening but it is what it is I guess. Still love the fish just wish I was seeing better growth.
 
  • Like
Reactions: tlindsey
To me water changes are "the" most impotent factor in promoting good growth, and I consider a 25% water change once per week barely adequate for health, much less good growth.
It might have been OK when the oscar was 2" or even 4".
But as the Oscars grow they put out more and more waste in the form of nitrate the bigger they get, and nitrate, and other metabolism by-products tend to build up with tiny water changes and that waste chemical soup can stunt growth. Filtration doesn't help lower nitrate, only water changes do.
If you want growth I would increase water changes to at least two 50% water changes per week, or better, even 3.
I would imagine if you checked your nitrate level at the moment , it might be 20ppm or higher.
On my tanks I tend to change 40% every other day, or when I have time, 25% per day, and this regime helps keep nitrate as low as 5 ppm, and have never had problems with growth of any cichlid..
 
Did you even read my post? I change 75 percent of the water a week.... I do a 50 percent change on my day off then a 25 percent on a work day. Equaling 75 percent a week I know a 25 percent change a week isn't close to enough especially being stocked to the max.
 
It looks like you are doing everything mostly right. One possibility is stress from the JD but its more likely he has just had his initial growth spurt and is slowing down on the growth rate now. It will probably keep growing and adding weight but very slowly, maybe too slow for you to even notice.
The only suggestion would be do both weekly water changes at 50%, wont do any harm anyway.
 
Okay I will sometimes I just don't have enough time to do 2 50 percent ones but I will try harder to make that happen. Its odd but the oscar is actually the tank bully the jd runs away from him daily. He's very passive the oscar is on everyone's case. And maybe he is just another slow grower I hope it at least hits 10 inches will see haha.
 
  • Like
Reactions: tlindsey
Up your water changes. I do 75% every three days. With this regiment I got an Oscar and a Saggitae out to 12in, Saggitae was a little longer than a year to 12, Oscar a little shorter.
Oscar I started with
20170605_181541.jpg
Same Oscar a year later
20180830_170959.jpg
Saggitae I started with
20180901_154201.jpg
A year later
20190527_143017.jpg
 
Did you even read my post? I change 75 percent of the water a week.... I do a 50 percent change on my day off then a 25 percent on a work day. Equaling 75 percent a week I know a 25 percent change a week isn't close to enough especially being stocked to the max.

35ppm nitrates seem pretty high, make sure its below 10ppm everyday.

stop feeding peas to the oscar. Pea protein can cause primarily insect/fish eating predators to spend more energy getting it through their digestive system than using it for growth.
 
  • Like
Reactions: Toiletcar
Will do like i said that's the highest its ever been in 7 months after I went on a 10 day vacation its usually kept between 5 to 15 ppm! Im going to up the water changes and I can do that. I was feeding him peas because people had told me it helps keep their digestive tract clean essentially
 
MonsterFishKeepers.com