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

[Mark_C]

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?

 

[ericrodriguez]

I think all depends on how much nutrients you going to put in!! Also the amount of fish will determine if they will need wch or not.

 

[amado]

I use to have a koi pond that grew water lilies
No water changes just water lilies clean the pond clear.

 

[horseplay]

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.

 

[DEL]

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.