[Steve Hampton]

I'm with Phil, your AC (activated carbon) was probably saturated and acting as biological media, when you removed it you probably removed a fairly significant portion of your nitrifying bacterial. You either have a bacterial bloom that will clear on it's own in a few days, or more likely the small ammonia spike from removing the AC has started a green water algae bloom. GW can appear milky white for several days before acquiring a green tint. If the milky appearance worsens throughout the length of the photoperiod, and it's better the next morning only to repeat the worsening phase again the next photoperiod then it's definitely a green water issue. Here's five methods that I've used in the past to eliminate GW. Blackout, Diatom Filtering, UV Sterilization, Live Daphnia, and Chemical algaecides/flocculents. The first four cause no harm to fish, the fifth one does.

Method No. 1

The blackout means covering the tank for 4 days, no light whatsoever is allowed into the tank during this time. Cover the tank completely with blankets or black plastic trash bags. Be prepared, killing the algae will result in dead decaying algae that will decompose and pollute the water. Water changes are needed at the beginning and end of the blackout time and NH3 should be monitored also.

Method No. 2

Diatom filters can usually be rented from your LFS. This is my preferred method. Personally, I use my Magnum 350 w/Micron Cartridge coated with diatom powder. Diatom filtering removes the algae and doesn't allow it to decay in the tank. You do have to check the filter often, if you have a really bad case of GW the filter can clog pretty quick. Just clean it and start it up again. Crystal clear water usually takes from a few minutes to a couple of hours or a worse case scenario a few days.

Method No. 3

UV Sterilizers will kill free floating algaes. They also kill free floating parasites and bacteria. Some feel they can be problematic for extended use in a planted tank, because they can cause the "breakdown" of some important nutrients. Too sterile of an environment may not be healthy for a planted tank. They are expensive and don't remove the decaying material from the tank, if you can afford to keep one they are handy to have around, though not as useful IMO as a diatom filter.

Method No. 4

Adding live daphnia to your tank. This can be a bit tricky. First you need to insure that you are not adding other "pests" along with the daphnia. Second, unless you can separate the daphnia from the fish, the fish will likely consume the daphnia before the daphnia can consume all the green water.

Method No. 5

I hate the last way, the flocculents stick to the gills of fish, while not killing them it does compromise their gill function for quite a while leaving them open for other maladies. It is also important to insure that your KH is at least 3 degrees before using a flocculent.

 

[Steve Hampton]

So, 4 days huh? Wont this hurt the plants/ fish?? Should I expect all my plants to be dead after this?

All you plants will do fine, if you have glosso it will probably have started growing vertically but a haircut and a few days under light will solve that issue.

What about leaving room light on only? Is that good enough?

That's fine. The tank is covered in such a way that no outside light should be able to penetrate. Just make sure you stop injecting CO2 and that you still have good air exhange...adding an airstone is a good plan.

What is the source of Green water? Something I added or not?

The direct cause is hard to say. Usually the culprit is having ammonia/ammonium in the water. This could occur due to a loss of biofiltration or by stirring the gravel and having some food or other decaying debris introduced into the water column. If you use solid fertilizers in the substrate then have a substrate disturbance that can cause green water too. Often the green water itself will solve the initial problem, meaning the small ammonium spike would be consumed by the green water. That's why it's usually wise to eliminate the green water first then do a water change and add back nutrients like your normal dosing routine calls for. The water changes are very important before and after the blackout.