Algae green or algae brown — there is something to figure out

I use NYC tap water to refill my aquariums.

First I put the tap water in an a jar and let it sit overnight for chlorine to evaporate.

The next day I can add the water to my aquariums as needed.

Here you can see two jars I use for this purpose.

On the left is a jar I use weekly.

Notice the common green algae growing in this jar.

You can see deposits of green algae on the walls and bottom.

I clean this jar of all algae deposits once a season or so.

I rarely use water from the other jar.

This jar is larger.

I use this water when I need a lot of water at once, to set up a new aquarium for example.

I noticed a brown algae grow in this jar.

It raises a question — why does algae grow with different colors in this two jars?

Is it because the jars are different sizes or different glass or one has a cover to reduce water evaporation or something else?

Let’s make some changes to see if it makes algae grow different colors.

June 11th, 2021

First things first, let’s use jars of the same size made of the same glass.

I washed both jars clean of any algae.

Refill jars with the same NYC tap water.

This jar placed closer to the window is covered with a lid that has holes in it.

I am not going to use water from this jar to refill aquariums.

Brown algae was growing here under the same conditions.

The second jar has no lid and placed on the same shelf about 3 feet away from the window.

I am going to use water from this jar to refill my aquariums.

So, I will add NYC tap water to this jar once a week or so.

Green algae was growing under the same conditions in this place but in smaller jar.

It takes weeks and months for algae deposits to build up on the walls.

Here you can see I use water from the jar on the left to refill aquariums on June 16th.

I prefer to add water in aquarium gardens through the holes in the planters.

Keep the lids on saves time and less disturbing for aquariums.

After refilling all aquariums I add NYC tap water into this jar.

And let the water sit in the open jar overnight for chlorine to evaporate.

About one month later on July 4th.

I don’t see any algae in the jar on the left.

Though, there are deposits of brown algae in the jar on the right.

So, let’s see what would happen if I cover the jar on the left and leave the jar on the right open.

And here is the jar on the right.

Let me show you the lid.

It is actually a type of planter I use for my aquarium gardens.

It has holes allowing air circulation while reducing water evaporation.

I am going to reset this jar.

Let’s clean all the algae from the walls.

And now I refill the jar with NYC cold tap water.

Let’s put the jar back on the same spot on the right next to the window.

This time I am going keep this jar open and use the water for weekly refills.

Here you can see I refill my aquariums using water from the jar on the right on July 7th.

Then I refill the jar with NYC tap cold water.

And the jar is going back to the spot next to the window.

About one month later on August 4th.

You can see green algae deposits in the jar on the right.

It’s time to reset this jar again for the next try.

I wash and refill the jar.

This time I cover both jars with lids.

And this time I am not going to use water from either of jars for refilling my aquariums.

Let it sit as long as it takes for algae to grow.

About 2 months later on September 10th.

I did not change water in both jars and both jars covered with lids.

And…green algae has grown in both jars.

It’s not what I expected…but it’s what it is.

Algae has me really confused on this matter.

Have fun and happy aquariums :)