Simple Math Question

[Jody]

When folks on this forum are talking about percentage water changes, are they referencing their whole system's volume with the sump included, or just the display tank's volume?

Example: I have a 40 gallon display tank, and a 40 gallon sump, so if I change half of the display tank's volume I am only removing 20 of 80 gallons or 25% of the total water volume.

I am sure this has come up before.

[Adam S]

I'd say whole system.

[Paul Sabucchi]

I consider whole system-ish. My tank is about 100 gal, I do not count the 1 or 2 gal of water in the canister filter and hoses but if I had a 40 gal sump I would definitely count that

[eugenefish]

I count the whole system too.

[bluelagoon]

If you have a sump,it would only be logical to add that to the volume/percentage.

[JamesW]

I have a 90gallon tank with substrate and wood and a 29gallon sump which is not quite full and has poret foam in it. I ball park at 100 gallons. It might be a bit more or a bit less but 100 gallons is a great round number for me to use!

[Jody]

The survey results are a bit mixed - I will start referring to total volume when referencing a percentage water change.

[gunnerschh2]

I have 3 sumps & change water with a syphon. If I was to include sumps I would have to use a pump. I think the question is a little misleading. I have one sump that is 90 gal. & I would not know %. of water.

[Jody]

I have 3 sumps & change water with a syphon. If I was to include sumps I would have to use a pump. I think the question is a little misleading. I have one sump that is 90 gal. & I would not know %. of water.

So if you changed 50% of your water today, would you be talking about only your display tank's volume, or would you include the sump's volume as well?

What makes you feel that question is misleading?

[DiscusBR]

So if you changed 50% of your water today, would you be talking about only your display tank's volume, or would you include the sump's volume as well?

What makes you feel that question is misleading?

Your questions is very clear and there is nothing misleading about it. The mixed poll results show that there is a need to adopt a more standard language in this forum (maybe the moderators can even add a sticky or something): the calculation of WCs has to be based on the water volume of the whole system, including sumps.

[Jody]

Your questions is very clear and there is nothing misleading about it. The mixed poll results show that there is a need to adopt a more standard language in this forum (maybe the moderators can even add a sticky or something): the calculation of WCs has to be based on the water volume of the whole system, including sumps.

Thank you, DiscusBR - I think it would be helpful to know that standard. It may already be defined on SD, and I just have not found it!

[bluelagoon]

I don't see where it is misleading.Just seems some folks are not changing as much water as they thought they were.

[gunnerschh2]

If i change 80 gal. from a hundred gal tank then i feel i'm doing a 80% change. I don't care whats in my sump. I don't count that gal. in sump when i use the 1 discus per 10 gals. I under stock to try to advoid problems. I's not easy to explain my self on a 30min. typing spree.

[Jody]

If i change 80 gal. from a hundred gal tank then i feel i'm doing a 80% change. I don't care whats in my sump. I don't count that gal. in sump when i use the 1 discus per 10 gals. I under stock to try to advoid problems. I's not easy to explain my self on a 30min. typing spree.

Thank you for your addition! Just curious, how large is your sump?

[gunnerschh2]

Largest esopps forgot the gal. To find the real gal of water you would have to siff seperatly % then measure the real gal. because of displacement & a sump is never full of water. Also i never shut of pump in sump till last min. & siphon a little more water that i don't count. This poll is close & there were 6 other people that i would like to hear from that voted the way i did . I just rested my finger in the fish room & asked my 11yr. discus if i was doing ok on the water changes & he gave me an atta boy!!!!!!!!