I have *BLACKIE*, it is about 28 cm long and definitely keeper of the tank. It was way meaner when it was younger. However it is so big now that the littler guys just avoid it. It never hurts them, it herds them around. I have two silver dollars about the size of a real silver dollar, one plecostomus and 6 different types of catfish including two albinos. It doesn't bother the catfishes. It seems it wants the silver dollars to live in one part of the tank and that is all. They eat at one end and I feed it at the other end. So it doesn't feel the need to defend its food. It is quite a character and very funny. It will interact with you. I can put my hand up to the tank and it will come right over and lay beside my hand. It is awesome and I adore it. By the way, they are in a 250 L show tank. I should be considering a bigger tank. I have given up on real plants. I now have soft silk types. It moves them about willy nilly. It rearranges the whole tank to suit its moods I think :-)
I have a black shark fish that seems to be very intelligent and friendly. He has learned to do a trick of sorts and even to play games of hide'n'seek with me. I agree they can be territorial and can become agggressive. My fish (I call Wishy) has eaten a few others in the past seven years, not by my choice, but I do find him rather entertaining and personable. I love him is the bottom fact and I think that in his fishy way he rather likes me, not just because I feed him either.
I have a black shark named sharkey and he is 10 years old. I have him in a 200 L aquarium, but I am going to put him in a 470 L tank. He is 61 cm long right now. He has an attitude and will let you know when he is not happy by splashing the water in the tank. The only fish that have survived in the tank with him are two catfish. He sometimes chases them and tries to nibble on them but they are OK. They just stay close to him.
I have a Black Shark who is about 30-35 cm. He's a great fish. Very friendly. He loves being the boss, but he's not vicious. I find it interesting to observe the politics in the tank between him and the Red Tailed Barb who shares the tank. I inherited the tank and fish more than a year ago from my nephew who has taken on the responsibility of saltwater fish. He said the shark was very aggressive and would pick on my Barb, Pleco and Catfish. What I observe is quite a bit more complicated. The Catfish is just crazy. He's not even part of the equation. The Pleco is sometimes kind of a jerk because he'll wait for the shark and the barb to be playing chase and he'll sneak into the Shark's hideaway (a large PVC pipe) and latch on. The shark gets very irritated and tries to bump the Pleco who is very stubborn and only lets go when the Shark gives up. Late at night the Barb messes with the Shark by snatching a bubble of air and releasing it into the Shark's hideaway. This continues until the Shark comes out to chase the Barb. Meanwhile, I have two petite Loaches who come out of hiding to play head games with the Shark. The Loaches look almost identical (names are Frick and Frack) and they capitalize on this by bumping the Shark on the tail to engage in a chase which they invariably win. Shark chases one while the other sneaks up behind and bumps him. This goes on for a while until the Shark retires to his hiding spot. I swear he must think that there's only one Loach.
A very large black shark I bought about nine years ago just jumped out of the tank and died. He measured 52 cm and weighed at least a few kilos. I raised him in a 510 L, then a 760 L tank with many other fish, and at one time with small turtles. He was very shy and not at all aggressive. A lovely fish. I was very sorry to lose him.
I recently lost my black shark named Waldo. I bought him at Walmart about 5 years ago, and he measured only an 3-5 cm in length. When I first put him in my little 40 L tank in my college apartment, I noticed he was not like other fish. He hugged the heater, and stood upright against it. When I would look into the tank, he would wiggle a little bit and peer out from behind his warm friend. Very cute. However, he gave me a few scares as these fish like to jump! One night, I awoke to the sound of my cologne bottles being thrashed around on my dresser. I jumped out of bed and quickly turned on the light. There was Waldo, gasping for air and knocking the bottles onto the floor. How did he get out? He rammed his head several times into the light cover and actually moved it aside to create an opening! He did this 3 more times over the years, but he only did it when he was moved to new tanks or relocated. Well, through all of his clumsiness over the years and surviving, he did grow quite large. Too large, in fact, for a 200 L tank. Since he was aggressive towards other fish, he had to live alone. That always saddened me a little, and I wish I could have done more for him. He made the entire aquarium a mess, and it was hard to keep up on maintenance. Though he died relatively young compared to some of the other black sharks on this page, he did grow to 45 cm in length, about 18 cm high, and weighed in at 1.5 kg! He now rests, buried on the shore of a large pond located across the street from my house.
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