180 gallon Freshwater tank

Question
We are experiencing a greenish hue to the water that was very bad a few days ago.  We performed a water change- about half.  Here is where we may have made the mistake.  We dont have a lot of fish but one did have babies a few weeks ago.  We thought by changing the water down that this would help with the consistancy of the greenish water.  We wiped down the inside and didnt see anything that appeared as algae but more like a film.  It is two days after the water change and it is getting back to where it was before witht the cloudy greenish color.  Help us decided if we should start this tank over or wait it out to see if the phosphate pad we placed in the canister filter will help.  We treated the water with a nitrate prime recommended by the fish store.  We are trying everything they ARE RECOMMENDING AND NOW I THINK WE NEED AN EXPERT.  Thanks for your help.

Answer
Green water is due to algae, single cell...cut the light source back..
save money, skip the nitrate prime, that has nothing to do with green water....skip the phosphate pad...is it HBH?
don;t work in this app.
this is a large tank to restart...so..cut back on the feeding..control the light source, window, tank lights whatever...
if you remove the light source the green algae can;t survive...the cloudy is new tank syndrome..due to the 50% water change, that just fed into the problem by putting raw material back in the system...
give it 5 days or so, if you watch the food, dont add more fish and control the light it should clear up...if you have an established filter from annother tank, squeeze the cart.or media into your 180 to seed it with "good guy" bacteria.
after this settles down, depending on population and species of fish, a 10% once a week will be fine...
good luck..