My silver arowana in 4500 gal

thebiggerthebetter

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My answer will be speculative. I find silver arowana personalities (prior histories, health, etc.) vary enough that the gender behavioral differences (other than pertaining to procreation) seem to mostly wash out. Some trends seem to hold, like in a community of several (4+) specimen, the territorial aggression seems to be mostly intra-gender, not so much inter-gender although the females can sometimes be cranky toward the males too but not vice versa. The appetite of the mature females growing eggs in their body seems to exceed the appetite of the males, even though the females appear a bit smaller... but I may not have enough data yet to claim the size disparity.

For juveniles in separate tanks, which is your case, it'd be hard for me to say much, because I see a variability in arowana temperament, energy, behavior. I think I know exceedingly little yet to be helpful. Rarely do I get chances to enjoy the fruit of our labors and sit down and observe the fish a good while.
 

thebiggerthebetter

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No, yellowish water because of tannin plus blue-painted walls = green color :)
 
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thebiggerthebetter

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A couple of threads talking about possible sexual differences in external features of silver arowana with our input as well:




Sudden unexplained skittishness:


 
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thebiggerthebetter

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I was asked two questions by a peer:

[1] How big a currently 10" arowana needs to be to be safe in a pond with a 2' female?

[2] Not sure my gender predictions are accurate - ventral fins seem to be generally longer until ~18", then grow & shrink with... season? mood? Big "girl" in the outside pond had longer fins when she went in, they shortened notably in the fall/winter & now they're getting longer again. Never been luxuriant like on your girls, though.

My answer:

I personally would not combine arowana of sizes that are too different, especially if there are just two - two is always the worst scenario. I think the sizes should be comparable, so that the smaller has a chance to get away with only insignificant damage caused by the bigger. The closer the sizes, the lower the risk. Also the tank size and scape, if any, will play a role in the eventual cohabitation or the eventual death-by-bullying of the smaller arowana. Observe closely. If the smaller aro behaves unnaturally, like doesn't swim at the surface, that's the sign to take it out.

I'd say 18"-20" vs 24" can be tried with vigilance and caution. We've done it many times successfully (some scales will go missing from attacks but not too many and not too often that the fish needed to be separated) but in large enclosures, e.g. 4000-5000 gal.

I've started paying attention to our arowana pelvic fin lengths only after having them for several years, after maturation. Hence, I've not much firsthand experience with what happens with them before that. It seems the difference is not so clear with younger fish from the photos on internet, and the thread here on the MFK where I was questioned by a peer (linked above), and from watching 2 our younger rescues grow, as the difference is with our adults, where the female fin length exceeds the male fin length most obviously at all times of year and ages and moods.

By fin I mean both the rays and the extension. Sure males fight and may bite off the extensions every now and then but even the rayed portion has been smaller in our males in my experience. In any case, EVERY time, over many years and specimen, I looked at the fins on our males vs our females, I was satisfied that my observation held obviously true, no squinting required.
 

thebiggerthebetter

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Our current quartet of arowana, Flap the 10 yo male and three females Hsieha 8yo, Ylana 3yo, Beakerina 2yo, continue doing well:

 
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