Tank water turning black...

My tank water is turning dark black but i can still see the fish and it honestly looks normal but when i did a water change today i noticed that the water in the bucket had a black hue to it... my fiance is changing all the water right now and i transfered all the fish to my hosdpital tank till i can transfer them to my new 100 gallon but i just havbe no idea what could have happened... like i said you can still see everything in the tank and this didnt happen overnight... i havbe somewhat notice the back ground getting darker and darker and the plants and rocks dont look as bright but i was very surprised when i changed the water... if any one has any ideas that would be great i just dont want this to happen again... i used quick cure about a month ago and i know it doesnt have to have a water change after but i have done a 30% and a 20% water change since then and didnt have this problem with the water... i havent added any new fish and havent changed the declorinator or salt i use or anything so it cant be a reaction to that. my fishg are all acting fine also, no out of sort behavior at all and i diont have a tv in my living room so all i watch is them... no disease, fungus, or bacteria syptoms and all my levels are absolutly fine... i used quick cure as a precaution cause one of my devils was scratching but my female had her tube down also and i just rearranged the rocks so i concluded that he was just marking his terittory. i added new carbon to the filter once i did the first water change after the quick cure treatment, could that be it. should i do any type of treatment to these fish in a hospital tank before adding them to my 100 gallon or anything... any imformation will help... thanks

only thing I can think of is could be the carbon or substrate... you suppost to rinse the heck out of it before the first use... hope you did.... it has to be something that is dyed black and releasing its color.... water just doesnt turn black if you mix salt and quick cure in it... if anything maybe a blueish tint but the carbon shouldve taken care of it... well unless the carbon is the problem... after you do this 100% water change everything should be back to normal... I would make sure to rinse the carbon and vacume the substrate before refilling. Good luck.

Is it possible that the black color is actually a dark green?

sounds like an algae problem to me. whats your water change schedule and how long do u keep the lights on the tank?

Do you have driftwood in the tank?

it was black definatly... i change water once a week and only have lights on for like 4 hours a day so its not algea... it was the actual water that was colored... and no driftwood in the tank.

sounds bad. id get the water checked and see if anything changed from the source.

Im still thinking its that new carbon, really thats the only logical explanation if you havent changed substrate, or decor and it just started happening...

Carbon will tint the water black if its a fine powder. But you essentially filter that out with its source given time. tanins can also tint the water brownish or tea colored. some substrates can leach color in to water, turface in particular can do this. Unsealed decor not for aquariums might as well... as well as yarn dyes (if your into killifish breading) . if you have none of those i would drain and clean that tank. if your water is black something else is in that tank causing that problem maybe a kids toy or something.

thankfully i have not had this problem agian and i do think it was from the carbon or a color leach of some kind but i took down the 55 that it happened to and just today got my 110 and 75 gallon new tanks fully set up and i have not had this problem... thanks for all the input and i will put community tanks pictures up later with a fishy update... alot has changed since i joined just a little while ago and im falling in love with my new tanks more more... i already wanna upgrade again but i think this size will do for our apt for now