cloudy water!!

Question
QUESTION: Hi
I m completely confused about why my marine tank has gone cloudy. It has been set up for 8 months and has just gone cloudy in the last week. The tank isnt overstocked or over fed. I have an internal filter and external filter. I never had these problems with an undergravel so have now put one in and have now put external filter tube down it to give extra filtration. I ve had marine fish for 15 years and never had this before.
I would be extremely grateful if you have any suggestions or solutions as i am really worried about the fish although strangley they are all healthy and breathing normally and eating!
Thanks
Mark

ANSWER: hey Mark

ive just gotta ask you a few questions so i can narrow down why you are having cloudy water. Do you have any live rock? If so, how much? is the rock cured?

One more thing, do you have a saltwater test kit? if you do, how is the ammonia reading?

---------- FOLLOW-UP ----------

QUESTION: Hello

Thanks for replying. No living rock and had the same rocks for years. I also did another water change of 25% which helped clear it but within only one day is was bad again!
Need to get an ammonia test done today as havent done it yet. There is a green tinge to the cloudiness also. so was wondering in something had been done to the local water supply to make it high in phosphates or something but i m still just guessing. I have an 8" Lipstick tang, 7" Regal tang, 3" valentini puffer, 3" scopaz tang and 3" clown fish in a 4 foot by 18" wide by 2 foot high tank so its not overstocked or anything. The tank isnt too close to a window either. I m so confused about what it could be but will get water tested today and see what they say.

Answer
Hey again

Its possible that the phosphates in the water are causing the algae, but are you using RO (Reverse Osmosis) water? Usually tapwater has bad minerals and phosphates that arent good in saltwater, and RO water has none of these. Tapwater can cause hair algae and cyano outbreaks

good on getting the water tested, see if theres any ammonia