Cloudy green water

I have two Fluval SPEC 5 gallon tanks. Mine is a few weeks more cycled than my son's and mine is doing well. His on the other hand, has cloudy green water. I've taken measurements many times and they always come back the same. Nitrate and Nitrate are 0. pH is 7.5 and kH is 120/180 and gH is 180. Yes, they are slightly high, but both tanks read this and this is what my water is, plus my tank is a control (in some sense), and the fish are doing well (seemingly in both tanks).

I know in his tank, he has diatoms. Yesterday, I did a 50% water change using a vacuum. Water was marginally clearer, but has somewhat returned to the same cloudiness. So to be clear, yesterday's water change / vacuum did make the water clearer by some, but did not make it crystal clear like mine, and today it has increased some cloudiness, but not to the level it was prior to the change.

Just to check, I took some water from my tank and his tank and compared them in two glass jars. His was definitely colored/tinted (green). Ammonia is zero (used a tube kit).

I'm thinking of doing 50% water changes over the next few days. But maybe this is an imbalance that is due to a not-fully cycled tank? I'd say maybe we're at 8-10 weeks?

Edit: My son's room has two windows, but does not get direct sun, and they are covered in blackout curtains. The tank is away from the windows, and the filter side, which is blacked out, is facing the window, so there is no direct sunlight and very little indirect.

Several points to keep in mind. First, diatoms are common in many (but not all, certainly) new setups because the biological system takes a few months to stabilize. Floating plants (live) would help a lot. I will assume the "algae" really is diatoms, if it is, this easily wipes off with your fingertips. If it does not, it is another algae.

Second, green water is due to unicellular algae in the presence of (usually) strong light and nutrients. Floating plants again will provide the most effective course. And reducing light, tank light and ambient room light. This latter does make a difference; several years ago I finally discovered that the reason for an increase in black brush algae in my larger tanks every summer was due to the increased daylight--both intensity and duration--entering the fish room. I blocked the light from the end windows completely, problem solved for several years since.

The cloudy tank does not look that green to me, but no matter, whether this is green water (algae issue) or a bacterial bloom, reducing nutrients and light should help, but again floating plants really will benefit.

The cloudy water reminds me of a bacterial bloom. Just to add onto Byron's post, if your son is overfeeding the fish then there would be an imbalance of nutrients in the water that could contribute to the cloudiness.

Actually, I've been feeding his fish with his school schedule, and we coordinate to ensure we are not both feeding, and I have learned the correct amount of food after trials and errors of earlier this year.

I can say that I know that his tank DOES have diatoms, because in another thread I learned about those, and they are brown and wipe right off the plant leaves and tank walls. I can say for certain there is very very little sunlight in that room. He has blackout curtains and they're nearly always shut. The light is not on much either as he's not home. He leaves the tank light on when he leaves for school and I turn it off in the evening.

The water is cloudy, and the picture doesn't really show the green much, but comparison of tap water in a clear glass to his tank water in a clear glass shows that it is cloudy, and slightly green. But it isn't seeming to affect the fish. I'm not sure I have room in a 5g to get a floating plant.

Maybe this will all go away in another month or two?

The tank light seems to be on a bit too long probably. Use a small timer you can get in the hardware-type store for a lamp, and have the light on a schedule. It does not matter when this is, so long as it is consistent each day and the room is light when the tank light comes on and when it goes off. Suddenly light on/off is stressful to fish, as is an inconsistency every 24 hours. Has to do with the circadian rhythm inside all animals, including fish which have a higher sense of light than some animals including us.

So outside of reducing light, and adding a floating plant, what should I do?

Will this go away eventually on its own?
Are my fish in any harm now?
Are they able to breathe?
Will more frequent water changes make it worse or better?

FishyJoe said:

So outside of reducing light, and adding a floating plant, what should I do?

Will this go away eventually on its own?
Are my fish in any harm now?
Are they able to breathe?
Will more frequent water changes make it worse or better?

Click to expand...

Reducing light and adding floating plants are both major changes. To want to establish the balance of light and nutrients so plants benefit and algae is thwarted. If there is a problem in the balance, it is not likely to "go away" without you interfering and correcting the balance. But reducing the light and adding fast-users of nutrients (floating plants) are game changers.

Water changes may help or may worsen it, because there are organics in the tap water and these feed algae. Generally fish are not harmed by this, though intime there can be issues with carbon and ammonia, so it is best to restore/establish the balance that keep this in check.

FishyJoe said:

So outside of reducing light, and adding a floating plant, what should I do?

Will this go away eventually on its own?
Are my fish in any harm now?
Are they able to breathe?
Will more frequent water changes make it worse or better?

Click to expand...

You might be surprised at how well those changes work. I was starting to develope some algae. All it took was reducing the amount of light by one hour to rein it in.