overnight change of watercolour

Question
Hi Christy, We've had our 60 litre tank for a few years now, with basic goldfish and the odd weather loach, mountain minnow and black moor.  Last week we bought 2 new oranda's both of which died within a day and then we lost a loach and a big 3 year old goldfish. we treated the water last week with anti fungal drops (as usual in the circumstances) this morning when I turned on the light the water was very yellow...  Any ideas to what this might be? we don't have any real plants, no dead wood and tank is not in direct sunlight.

Answer
Hi Becky
A lot of those medicines will change the water color.  I don't know why it would show up a week later though....that's strange.  How long are you leaving the light on in the tank?  It may be an algae bloom going on, usually that's green though, but sometimes depending on the lighting and the wall color behind the tank, can give a different color appearance.  

Try doing a partial water change, and you can also try adding some carbon to the filter to see if that'll help remove it.  

I have a question, were the fish showing signs of a fungal infection?  Or were you using the meds because of the fish deaths?  I think your problem with the deaths, was what's called old tank syndrome.  Your tank is too small for all those fish you had, and usually what happens is the nitrates will go real high over time.  The fish can actually adapt to this, and everything looks fine for the longest time.  Then you add a new fish, and the new fish dies fairly quickly, because they can't handle the high nitrates.  Then what happens, the new fish that were added put out more ammonia then what the beneficial bacteria(the stuff that converts toxic ammonia and nitrites to nitrates) can handle, and the ammonia goes out of control and usually kills off some of the older fish in the tank.  

Sorry, I know you didn't ask for that last bit of info, but just wanted to explain what might be happening so you don't end up with more dead fish.  

Hope that helps and let me know if you have more questions!

Christy