The black and white "stones" are carbon and zeolite. The carbon is the black part while the zeolite is the white part. I would keep that thing out of my filter to let the bacterial colonies develop properly on everything else.
As far as water changes, think about what 5 separate 10% changes do.
The first one removes 10% of the contaminants.
Because of the first one the second removes another 9% of the original contaminants.
The third removes about 8% of the original contaminants.
etc.
The quick calculation of the remaining contaminants is to multiply 0.9 by itself as many times as you do 10% water changes. That will give you the fraction remaining. At 5 water changes it is about 59% of the original contaminants remaining.
Now do a single 50% water change and you have only 50% of the original contaminants remaining.
By doing it all at once, you have removed an extra 9% of the contaminants without using any more water. The 50% change takes more than 6 water changes to get that 50% improvement. Stop using wimpy water changes, they are not your friend or your fish's friend. It is far more work to tackle a daily 10% for a week rather than a simple 50% change one time and the resulting improvement is the same in the end. Some people do worry about doing large changes but people who keep really sensitive fish like discus are the ones that do tons of big water changes. They would accuse you or me of making my fish swim in their own wastes and I am far from shy about doing big water changes.
As far as water changes, think about what 5 separate 10% changes do.
The first one removes 10% of the contaminants.
Because of the first one the second removes another 9% of the original contaminants.
The third removes about 8% of the original contaminants.
etc.
The quick calculation of the remaining contaminants is to multiply 0.9 by itself as many times as you do 10% water changes. That will give you the fraction remaining. At 5 water changes it is about 59% of the original contaminants remaining.
Now do a single 50% water change and you have only 50% of the original contaminants remaining.
By doing it all at once, you have removed an extra 9% of the contaminants without using any more water. The 50% change takes more than 6 water changes to get that 50% improvement. Stop using wimpy water changes, they are not your friend or your fish's friend. It is far more work to tackle a daily 10% for a week rather than a simple 50% change one time and the resulting improvement is the same in the end. Some people do worry about doing large changes but people who keep really sensitive fish like discus are the ones that do tons of big water changes. They would accuse you or me of making my fish swim in their own wastes and I am far from shy about doing big water changes.
