• Folks, if you've recently upgraded or renewed your annual club membership but it's still not active, please reach out to the BOD or a moderator. The PayPal system has a slight bug which it doesn't allow it to activate the account on it's own.

Speculative discussion, PO4, N2, N3, and water changes


Staff member
Officer Emeritus
NJRC Member
So, quick thoughts for a discussion...
8-10g freshwater tank
Kids haven't changed the water in ages
Saw the half evaporated tank today
Got me thinking... but first off, the tank looks great, plants and fish seem quite healthy.

So, half the water evaporated over what I assume is weeks.
I'd assume that with 1/2 the water, the levels of phosphate and nitrates would be much more concentrate.
I know the phosphate won't hurt the fish, though it may cause algae, but it isn't, and the plants are growing like weeds.
The nitrates are consumed by plants and produce O2 for the fish, which also seem quite healthy.

So. I topped off this tank, now diluting the existing nitrates and phosphates by 50%, which got me thinking...

Lets assume enough bacteria that ammonia is being processed efficiently, nitrite is converting to nitrate, and nitrate and phosphate are being consumed.
With sufficient plant growth in the aquarium, is there any purpose to a water change?


Staff member
Board of Directors
NJRC Member
I use to have a koi pond that grew water lilies
No water changes just water lilies clean the pond clear.


NJRC Member
I have a freshwater tank. 40g. Maybe water change once a month. Low light plants doing great so are the fish.

Water change for fish is like we open the window to get some fresh air. Fresh air makes us happy.


Vice President
Staff member
Board of Directors
NJRC Member
I haven't done a WC in my tank in about a month. My acros are growing like crazy. I do run a cal rx though which definitely helps. Stability is key.