Well, it's been quite a few years since I had a red-tailed shark so I'm not sure if this is normal.

Yesterday I replaced the second internal filter on my tank with a tetratec EX600, this means that the water in my tank is pretty calm now compared to when it had the two large powerheads.

Since I changed this filter (I placed all my old media in the new filter so it would be ok) my red-tailed shark has been pretty lazy, he sits on top of his bogwood cave until a barb comes within a few inches, then he chases it away and patrols around for a couple of minutes before sitting on his cave again

Other than sitting there being lazy he looks normal, no marks, no scratching etc.

In the past there has always been a strong current so there was no way the shark could sit still. Is this normal behaviour or something I should be worrying about?

Water stats:
Ammonia: 0ppm
Nitrite: 0ppm
Nitrate: 15ppm
PH: 7.6
KH: 6ppm
Temperature : 26*C

This post has been edited by maximinimus: Jun 17 2008, 06:22 PM

all your water stats seem fine. As long as you dont see it hanging at the surface (usually caused by lack of oxygen) or not even flinching when one of your barbs comes by (lack of interest or energy to protect territory could mean illness), it should be ok, just taking a rest now that it lives in a calm estuary instead of the fast flowing torrent

Probably just enjoying its new-found peace and quiet!

My shark tends to be a little lazy - it moves around the tank a fair bit, but at a slow, gentle pace. Apart from taking time out to hassle my CAE and do a few patrols of the tank, it mainly stays in one area, and isn't really too active.

I wouldn't worry about it, it seems fine. A change in behavior has to be expected along with a change in environment.