How Often To Do A Water Change

[fahrenheitfan1]

i know this i rather a noob question i am asking but i have a 90 gallon aquarium with very heavy filtration, so heavy in fact that is cleans my entire aquarium every 1.20 minutes, its a sump with a flow rate of 4000 gph, i test it weekly and my water conditions are always perfect, is it alright for me to do monthly water changes, since the parameters of the water never changes, even if i leave it for a month

 

[snazy]

Which parameters exactly do not change?
A larger tank can go longer with no water changes depending on the fish but there's a wide range of stuff that accumulates in a tank and can't be removed just by heavy filtration, it needs fresh water in to dillute it although being overfiltered may help to an extent.
Do you have a TDS meter?

 

[fahrenheitfan1]

the nitrate, nitrite, alkalinity, and pH are always at the right level, and i do not have a tds meter, i use a test kit

 

[snazy]

Then you wouldn't know whether to change the water or not and in this case regular maintenance is best.
Almost all tanks with adequate filtration and stock have the same nitrite, alkalinity and Ph with that difference that nitrAte rises. If your question is about nitrAte being the same all the time and therefore no need to do a water change, keep in mind that this is not the only indication to change the water. Nitrates in one of my tank go down to nearly 0 because of the plants but I still do 50% weekly water changes and I am actually dosing nitrAtes because of the plants. The rest of the parameters for me also stay the same with of course ammonia and nitrIte always being 0 but so do for most folks around here and it's not exactly an overfiltration advantage, just enough filtration would do it.
TDS meter(total dissolved solids) tests for the total quality of the water which includes everything possible in it, like nitrAtes, dissolved organics, minerals, metals, even dechlorinator or fertilizers added will raise it up, etc..., etc...Basically, unless you test for each indiviual possible thing to assess the tank water quality, you will never certainly know if a water change should be done or not. TDS meter has the advantage to show you the total quality in ppm, so it does help to at least keep the level constant and do a water change when it exceeds that amount or when it exceeds the tap water amount the least.

So to answer your initial question, not it is not alright not to do water changes based only on nitrIte, nitrAte, Ph/alkalinity test.

 

[fahrenheitfan1]

thanks, you were incredibly helpful, i actually just sign up today, so i am still getting use to the site, but you helped out alot, i think i will get tds meter now

 

[snazy]

They are not very expensive depending on brand of course. I paid around £19 for mine including delivery and they certainly help to get the idea what happens in the tank.