Hey everyone. I'm new here, and somewhat new to keeping fish. I'll tell you what I have first.
45gal freshwater, wet/dry filter. It's been set up for about 10 months.
No live plants, just gravel and fake coral.
The tank runs at 78 degrees. It gets no direct sun-light, but the hood light is on for about two hours a day.
I try to do a 20% water change every week, but it usually stretches into every other week.
My PH is always perfect at 7.0, my nitrates are always very low, and my nitrates hover at around 20, though I haven't checked this week, I did a very good cleaning, and it's probably a bit lower.
In the tank I have:
(1) 3in Silver-tipped shark
(3) 1.5in rainbow plecos (I can't find anything under that name on the internet, so I am probably remembering the name wrong. Very pretty under white light, blue body with red fins)
(2) 1in Ram Cichlids
(1) 3in Angel
(1) 2.5in Green Severum
I feed them tropical fish flakes, and on occasion, frozen blood worms.
Now, first off, I know that some of these get quite big and I will need a bigger tank if I'm going to keep them to their full size. I don't plan to keep them that long. When they get too big, I trade them out and get smaller ones. I also know that it's a very odd mix of fish. I watch them very carefully to make sure they get along, and I've never had any problems with aggression.
I also know that the silver-tipped shark will need a brackish-water tank as it gets older. Right now he's quite young.
So, here's the problem. Lately I've noticed the shark has been hanging around much closer to my angel and severum. Usually he ignores them completely and swims along the bottom. Now I will find him swimming right next to them, often so close that he is actually touching them and freaking them out. He isn't attacking them though.
I've also noticed that he will be swimming normally and them suddenly start thrashing around for a second and then go back to swimming normally.
Sometimes he will also lay on the bottom motionless.
Finally, I noticed tonight, white spots on his head, small, about the size of a grain of sand.
I checked all the other fish, and they are free from white dots and are all acting normally. It seems pretty clear that something is wrong with the shark though. Does anyone have any idea what it could be?
I would appreciate any help you can give me.