Aquarium Forum - View Single Post - 150gal no watter changes projects seems to be going well

beaslbob · 01-01-2010, 10:26 AM

Quote:

Originally Posted by zepprocker45

Topping off water in place of water changes isn't quite a true water change. When water evaporates, a majority of what evaporates is just plain old water. when you physically change water, you remove nitrates, ammonia, etc. (which is much more efficient) If you can keep your params in check this way, awesome, but if you notice a decrease in water quality, you may wan't to buck up and change some water in that monster tank. Have you looked into a RO/DI unit? This will save you time/money.

We know replacing evaporative water is not a water change.

so lets analyze just exactly what a system of water changes do.

assume:

1) the replacement water has 0 of something

2) That something is increasing at 1 per day.

3) That somemthing is measured as a linear concentration (unlike pH which is not linear). Like Parts per million.

4) and you are do water changes as some interval with the amount of change tied to that interval. 10%/every 10 days, 20% every 20 days, etc.

Where does the tank wind you when this schedule has been running long enough that we can no longer measure and difference just before any of the water changes?

Answer 100 times the daily increase under any of the water change schedules.

The formula is:

just before water change=(daily increase*days between water changes)/(1/fraction of water change) + whatever is in the replacement water.

Addiitionally the macro algaes consuming nitrates also returns oxygen and consumes carbon dioxide. Plus that process also returns carbonates consumed by the aerobic bacteria reducing the ammonia/nitrItes.

We see this in new tanks where after a few months newbies are shocked they have 60-160ppm nitrates and are extremely fustrated because they have done their water changes.

While you may have extreme emergencies with very high ammonia values where water changes are a good idea, those are extremely rare. I had one 3 years ago where I inadvertantly added a toxin that pegged ammonia to very high values in a matter of hours. And I lost one fish. What I did was get the fish out of the tank, dosed prime, and let the tank heal itself. Ammonia finally dropped down a week later when I rinsed my filter media. I presume that removed the toxin.

But that was the one time oppsies not normal operation. Under normal operation just get the macros in there and let them expand and condition the system. Just as this poster has realized, the tank will basically take care of itself.

And IME for years.

my .02