lighting and water

Question
hey nathan, matt here, how u doing today? i got 2 questions for u today. first a little info about my tank setup is i have a 55 gal tank with a wide variety of fish including congo tetras, rainbowfish gouramis,angelfish,catfish,loaches,sharks,plecos,and that pretty much sums it up just diff kinds of each.and i have a t5 light on it which i leave on for 7 to 8 hours a day. so my first question is that i went out of town this weekend for 3 days and left the light off and when i came home and switched my light on all my fish looked horrible!! most of them looked not far from dead they were just all very discolored and rough looking! my bala sharks and roseline sharks were white as a ghost and laying on the bottom which they never do of coarse. so i was just wondering if the light being off for a couple of days really had that much affect on them? cause now i have had the light on for about an hour and all their color is coming back and they are starting to act normal again. so ur thoughts on that?      and my 2nd question is a kinda hard to explain but i'll try!  looking at my tank the water is very clear and you can see some bubbles which my filter causes where the water falls in (which i no i want!) but if you get rite up next to the tank and look close it looks like very very small bubbles swirlin in the tank all over, but i don't really know if its bubbles? the best way to describe what it looks like is when u mix warm water with salt to gargle with and you stir it up real good and look at it and you can still pretty much tell that its salt water, thats what it reminds me of. and i do not know what it is or if i should be concerned?        i always check my water regularly and its fine   ammonia 0   nitrite 0  nitrates stay below 25   kh is good and  gh  is good   so any answers you may have is very much appreciated!! (if you can even grasp what i'm trying to explain to you)  but thanks for your time man!!!!

Answer
Hey Matt,

Fish actually need light to be in optimal health. The fish were likely stressed by the inconsistent lighting, and as a result, they became lethargic and lost their color. The light also enhances the fishes' colors. don't worry, within a day or two, the colors will come back to normal. Also, if you didn't feed your fish, or if you fed a vacation block, that may also be part of the reason, as fish temporarily lose their colors as a result of inadequate feeding.

I know what you're talking about - I've seen it in some of my new start-ups. The bubbles are not a concern - they will simply rise to the surface and pop (eventually). These bubbles are OK, and are natural. However, if a 'mist' of bubbles collects at the top of the tank, or somewhere else in the tank, and doesn't go away, it may be due to the fact that your water is rich in organic matter (which is undesirable). The substances coat the bubble, making it harder to pop. 10% daily water changes for a week will solve this problem.

Good Luck, and happy fishkeeping!