Query on my silver arowana

Question
Hello Ron,

After a month of cycling my new tank, I have bought 2 baby silver arowanas (6-7inch) yesterday and brought them to their new home. Along with my Silvers, they have tank mates. Pair of tiger oscars, pair of electric blue convicts, one blood parrot, one green terror and one pleco in my new 185G tank. Filters used are UGF with 4 lift tubes, submerssible pump (1200 LPH) connected to a PVC based under the gravel made from a DIY (kinda like a Reverse UGF), one DIY in-tank canister attached with another powerhead of same capacity (1200LPH) and one xternal canister. Only one thing bothers me.

Just this morning I noticed that both my silvers are pretty aggressive towards each other. Although I dont see any signs of damage on their bodies, I am just starting to worry about them that they would really end up hurting each other and killing one another. However, when I monitored them closely, I noticed that both of them are biting each other vice versa. One silver would swim freely on the left side and one on the right side. But, when their paths cross, they start to slow their pace and swim pass each other closely side by side. Then I would see that one silver would bite the other one first. Then again, once their paths cross, and do the same side by side glances, the other silver returns the favor to the one who bit first. Then after a couple of rounds, one silver would tilt sideways and let the other bite its stomach and anal fin. And the same would happen again vice versa with the other. Its kinda strange but can it be that one of my silver is a female? I am kinda confused and worried. Please help.


Thanks,
Chris.

Answer
Hi Chris,
 I really doubt if this is mating behavior. They need to be three times that size at least before they can mate.  You are right to be concerned.  They could easily hurt or kill each other.  That is why most people keep either a single one or a group in a very large tank (e.g., 300+ gallons). I am also concerned about the oscar.  I assume that it is a small oscar, much smaller than the arrowanas, otherwise, the oscar will certainly try to eat the arrowanas at some point.  

-- Ron C.
  rcoleman@cichlidresearch.com
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