Well, i've had one yellow cuda live for almost two years before it died and it lived in a 20g long the whole time (do not pester and complain to me about the tank size. I couldnt upgrade due to parents dominant decision of not allowing me to go bigger and i originally wanted a 55g at least for this guy). It could of lived even longer but my problem was a the arowana i had with it that my cousin gave me at 4 inches. The pair was fine for the first 10 inches of the arowana. The cuda was bought at 2 inches and became a 6.5 inch. I've bought two other yellow cudas through the two years to build a small school but both died. My first cuda was successful and after a year (5 inchbes), it became an aggressive feeder and will feed infront of me after a year and being a solo cuda with my tank mates that have passed (sunfish, LMB bass, striped pike characin, small bicher, eclipse catfish, and a few other fish). I didnt get technical like you other expert aquarist. I raised mine out of enjoyment, favoritism of yellow cudas, fun, and desire. I fed it guppies to start but once it hit around 3 inches i started feeding it rosy minnows and around 6 inches small goldfish were edible, but i found 2-2.5in rosy minnows work best and my cuda favored them over the goldfish. The minnows provide better and easier swallowing for the cuda. Cuda died from unknown causes but for sure the 12 inch arowana, who later found a small crack by the filter and jumped out and died at 14inches). After two years i've picked up three just earlier today. Two of the three i picked up today are slowly dying. Once again, within the first week is the toughest for keeping these cudas from dying from fin rot and unknown causes. Will be heading back to the pet store tomorrow for hopefully two new ones. I kept my water temps at around 80-82 F. If you're planning on getting some, i suggest you get your tank all set and ready and running for a two weeks for new tanks. Do frequent water changes, although i mainly only did monthly 50% water changes with my first cuda. And ALWAYS ALWAYS keep medications for fin rot and fungus on stock. It's a must to have medication because the first two weeks are tricky.
Here is my first cuda and the only one to live for a long time. It was very fat at this time and around 5.5 inches here
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As you can see, bottom, still in a 20 long, this was a few months before the cuda died. it became smaller because of the appetite and food competition of the arowana (IT's common sense to remove the arowana after 9 inches). The cuda stopped feeding for a few weeks and died from food deprivation. You can also see the big problem i had with my cuda was its mouth rot because it swims against the glass. (6 inches here for the cuda)
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If you wanted to see a video of my cuda here you go. This video was when the cuda became an aggressive feeder and the arowana was a new addition. Very aggressive.
https://www.youtube.com/watch?v=H5I4N-HIPD4&list=UUwK_kWQlZF0qMsdatXbQdug