Water changes for 90 gallon Oscar

suprd71 said:

The original question... FOR THOSE WHO HAVE KEPT AN OSCAR...... obviously some respondents have not.

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The original question was actually for those who have kept a single oscar in a 90g aquarium, either alone or with dithers...


Not that it actually matters, because regardless of whether the waste comes from a single cichlid in a 90g or a million tetras in a 500g the principles are still the same; you change your water based on the chemistry and test results. A single adult 12" oscar (because realistically that's about as big as they ever get) is a solid and messy fish, but it still isn't a huge load on 90g of water. I would put money on it that a single adult oscar (and a few dithers) would thrive in a 90g with 50% weekly water changes, provided your tap water is ok.

I have never done more than a 50% water change on a tank ever. Even grow-outs, or during treatment. I'll do 50% daily if necessary, but have never felt the need for more than that....

Natimus said:

The way these things progress on forums it won't be long before a 12'X4'X4' tank will be "required" to "humanely" keep a single Bolivian Ram.

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I thought that was already a thing? I keep all my rams in separate 12x4x4s wouldn't want to Overstock by keeping two together lol just messing



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David R said:

The original question was actually for those who have kept a single oscar in a 90g aquarium, either alone or with dithers...


Not that it actually matters, because regardless of whether the waste comes from a single cichlid in a 90g or a million tetras in a 500g the principles are still the same; you change your water based on the chemistry and test results. A single adult 12" oscar (because realistically that's about as big as they ever get) is a solid and messy fish, but it still isn't a huge load on 90g of water. I would put money on it that a single adult oscar (and a few dithers) would thrive in a 90g with 50% weekly water changes, provided your tap water is ok.

I have never done more than a 50% water change on a tank ever. Even grow-outs, or during treatment. I'll do 50% daily if necessary, but have never felt the need for more than that....

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Again I respectfully disagree, and what I state is based on going on 45yrs of Oscar keeping. Oscars can far exceed 12ins. I currently have 4 that are well over the foot long mark, the longest about 14 and just 2yrs old. I have had over a dozen Oscars in my hobby life that have exceeded the 12in mark, and many live 12-15 yrs. The keys to this are tankspace, pristine water and quality diet. A 12in Oscar in a 90g tank is a big bioload contributor. While a 50% weekly water change will keep the fish relatively healthy, it is most probable that the fish will not reach its maximum potential of growth or longevity. A big Oscar will degrade water quality much quicker than most any other similar sized cichlid, thus the need for more frequent and larger volume water changes.

Sorry for the sidetrack, but I'll believe that Oscars get over 12" the day someone posts a pic of one lying on a tape measure. Surely after the decades of being kept in captivity there should be countless verified pictures of 14-16"+ Oscars, can you find one?

I did some searching, and the average size Oscar caught in the Florida canals is 10". Is the average aquarium specimen really likely to grow considerably larger?

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David R said:

Sorry for the sidetrack, but I'll believe that Oscars get over 12" the day someone posts a pic of one lying on a tape measure. Surely after the decades of being kept in captivity there should be countless verified pictures of 14-16"+ Oscars, can you find one?

I did some searching, and the average size Oscar caught in the Florida canals is 10". Is the average aquarium specimen really likely to grow considerably larger?

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Well, I'm certainly not laying any of my Oscars on a measuring tape to prove anything. Perhaps you should visit a quality, respected site dedicated primarily to Oscars. Oscarfishlover.com or Oscarfish.com Maybe after a couple dozen Oscar folks from either site confirm that any well kept Oscar can easily reach 12ins, and possibly in a year, well, just maybe then you change your opinion?

Oscarfish.com, sheeh, been a while since I visited there!

http://oscarfish.com/oscar-forum/memberlist.php/mode,/sk,c/sd,a.html#memberlist

I'm not expecting you to pluck one of your fish out and measure it just to satisfy my curiosity, but you must admit that it is rather strange that given the huge number of people claiming to have >12" oscars, it is damn near impossible to find a picture of one on or beside some sort of measure to clearly show the size. I have no doubt that the odd exception may grow to over a foot in length, but I don't believe it is the norm. I would think that 12" +/- 1" would be an accurate max size for a hobbyist to plan for, anything bigger would be an exceptional fish.

Here's the site where the Florida Fish and Wildlife Conservation Commission state that the average size oscar caught in the Everglades is 10".
http://myfwc.com/wildlifehabitats/profiles/fish/freshwater/nonnatives/oscar/



Convict360, I'd certainly be interested to see that thread, I'm sure big water changes would be great for your fish, but I doubt they will be necessary. It certainly won't hurt to do more than is required to keep the nitrates low, I just changed ~20% (which is big for me, ~400L) despite only reading 5ppm nitrates pre-WC...

Just saying, im no poster child for raising and keeping oscars. But mine is huge. Hes over 10". I have no doubts under ideal circumstances they could grow in excess of 12-14"

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About 60-70% with some cleaning on the weekend. 30-40% strictly water change midweek. That's on tanks with mid to large cichlids. Not as much when smaller.


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I have a single adult male midas in a 90 gallon. Filtered by two AC 500's. (old school 110's for the kids)

While not a messy eater, I think that part can be controlled with O's by what one feeds, the size of the feed, and the quantity of the feed. The more digestible the feed, the less one has to feed, which ultimately leads to less overall waste produced. I perform a 70% water change each weekend. My midas is as healthy as a horse, and could probably lay an ass whooping on a 16" oscar.


HTH