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I have an Iridescent shark(Sniffles) He is about 6.5 inches long in a tank that is way too small, I have 55 gallon tank that he can go into but there is a very big, Very hungry 15 inch Spotted bullhead Ameiurus serracanthus in that tank, Is an Iridescent shark of that size fast enough to stay out of the mouth of the Oversized porker.

15 inch Spotted bullhead Ameiurus serracanthus

My favourite bullhead, this one must be a brute.

I would not risk putting them together,could be considered a meal or will just be bullied...and if it would survive being in with this fish the 55 is already borderline as far as conditions needed for the Ameiurus (in my opinion) so you may have problems handling waste etc.

Birger

Excuse me for butting in, but a 15" fish in a 55g isn't "borderline" - it is way too small. It's barely large enough for the smaller at the size it is right now - and with care, that fish should reach well over two feet, which will need a MUCH bigger tank.

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Mats

If you put your IDS in there, my prediction would be the bullhead will eat it. Sooner if you underfeed or later even if you overfeed it.

On the side note: Nice big FL bullhead you got there. I assume 15" is TL, not SL. Although I can see it Birger's way, I'd tend to agree with Mats - your fish must not be able to turn around comfortably. For that, the tank width should be at least 2x the TL of the fish.

By saying too small even for the 7" IDS (irridescent shark), I think Mats meant that in view of its very active, constantly swimming lifestyle. Bullheads, on the contrary, sit mostly motionlessly all day waiting for the light to go off.

Sorry if you already know all this but the forum is an open space, so a superficially unneeded advice doesn't always go to waste. Also, Mats is right in that you will need a tank with an 8' x 4' footprint at the very uncomfortable least to accommodate your IDS in a year or two. Given its hyper activity, one would recommend keeping a fully grown IDS in a 12' x 6' at least.

According to the rule of "4L x 2L x 2L" where L is length of the fish (7" in this case) means a minimum size of 28 x 14 x 14, and assuming the size of a standard 55g tank is correct (48 1/4" x 12 3/4" x 21"), it is smaller than the minimum size by 1 1/4". Sure, it's not as desperate as the 15" fish which doesn't even fit in one direction of the tank.

This rule isn't set in stone, but clearly with a fish that has a potential to grow to at least 4 times it's current size, putting it in a tank that is barely large enough right now isn't really a suitable solution. Especially if it's a very active fish. Obviously, a 55g tank is BETTER than a smaller tank.

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Mats

Yes, bad word choice on my part...trying to imply that even though this fish is surviving it is not really healthy conditions and things can go wrong real fast...

Birger

Problem solved, the iridescent shark moves into the 55 gallon tank and is doing fine. The larger Bullhead has now moved into a 125 gallon tank and he is loving all the space. I know the Iridescent shark will outgrow the 55 but the Bullhead is almost 6 years old and by the time the Shark is big enough the Bullhead will have passed. How long do bullheads live anyway? I haven't been able to get a bullhead live over 3 and a half years before now.

I take it that you are using US Gallons and not Imperial (UK) Gallons?

55 US gallons = 45.8 imperial gallons.

So being UK gallons orientated; I have to agree that 55 gallon (US) tank is to small.

My bullhead was A.Nebulosus which i had from a 2" fish for 7 years & then gave to a friend with a bigger tank also with A.Nebulosus which he had for a further 5 years before he moved and lost contact with him.

I would presume you could get 10-12 years from yours so the ID shark could catch up size wise and cohabit the 125.

Good solution. I like it. How long is your IDS today?

I'd be surprised if bullheads lived less than 20 years, barring accidents and unusual health problems. The fact that yours have not lived past 3.5 years is, likely, telling that something needs improvement.