This got me thinking... so i wanna know what u all think lol

[giar]

Ok cool that answered my question..

So infact when dosing the med we need to consider the volume of water in the sump, and the actual volume of water in the display.

Agree the rock and decors displacement arent significant, but the displacement from ur media in the sump i think needs to be considered, what u say?

Then go Back to water change, when you say u do 50% wc, is it 50% from 280 or 350? I know the % is just the estimate and i believe people say it the % they drain from the main tank, and not include the sump or the entire system? But shouldnt the percentage they say is from the entire system?

 

[skjl47]

shouldnt it be 50% of the entire system?

u add 9 caps of prime to treat 450 gal system, and not just 300 gal display tank?

rock and decors displacement arent significant, but the displacement from ur media in the sump i think needs to be considered, what u say?

Hello; First I get your point. An empty tank and sump filled to the top has more water in it than the same tank with stuff in it and the sump. Question is how much difference. Only way to get an accurate measure would be to use known capacity buckets, say five gallons each, and count the number of buckets for the initial fill up. That way as the water filled in the spaces in a substrate, was absorbed into porous materials such as rock, filled the spaces in the bio media and so on, you get the actual volume.
If you fill with a hose it will be a guess. I suppose some sort of flow meter can be added to a hose such as those on portable fuel tanks.

Your point has occurred to me in the past and the best I have ever done is a WAG estimate on the volume displaced by the stuff in a tank.

I do not know what sort of media you have in a sump but your estimate of how much it displaces does not seem right somehow. I use media of very little substance for the most part. By that I mean stuff that has an appearance of a lot of total volume but actually has a lot of internal open spaces. Filter floss and the blue two toned sheets for example.

As for the actual bio media some I have used did displace a lot of water. Back in the 1970's I used glass marbles behind the filter floss. I had the marbles on hand and they were not so expensive. These had some spaces between the marbles but the glass it self was not porous.

I used some carbon for a long time. I could get fairly large bags back in the day. It was porous and not so dense. It had internal spaces and did absorb water. Even tho the adsorption ability was soon used up I felt it still was a decent bio-media surface. As a bio-media surface it can be baked in a house oven which seemed to cook out some of the organic material that clogs the pores. ( I now know the adsorption properties cannot be regenerated in a house oven).

My thinking is if you use a porous bio-media that it will not displace so much water as you have estimated.

 

[giar]

Agree... my media displacement is just an estimate. But i figure media like ceramic rings take up significant amount compare to k1 or bio ball.

But for water change, what is the right thing if u say u do 50% wc?.

If u do 50% wc from the display tank only it is not really 50% wc, is it?

 

[giar]

Well this topic aint matter actually just i find it kinda interesting and wanna see how people see this

 

[RD.]

In all scenarios, in a closed system such as an aquarium everything should be based on total water volume.

 

[giar]

So i am correct then that people who say they do "X" percent water change is wrong since most of them do not put the sump water volume into consideration of their fraction?

 

[RD.]

I try to not to make assumptions, such as every member stating they perform a 50% water change, owns a tank ran off a sump. As an example, I always assumed that in any/all situations regarding water volume, total water volume was a given, apparently not. I am quite certain that not all tanks owned by MFK members have sumps.

 

[TonyS20]

Agree... my media displacement is just an estimate. But i figure media like ceramic rings take up significant amount compare to k1 or bio ball.

But for water change, what is the right thing if u say u do 50% wc?.

If u do 50% wc from the display tank only it is not really 50% wc, is it?

When someone says they do a 50% water change, it doesn't really matter if its not a 'real' 50% water change really.

The whole point of water changes is to keep tank parameters in check. If that 50% water change from the main tank keeps it in check then it doesn't matter if its not a real 50% water change.

If the 50% WC from the display tank doesn't keep the parameters in check then just do 75%.

I wouldn't say the sump even needs regular 50% water changes. A big part of water changes on the main tank is vacuuming substrate and removing waste/uneaten food from it and or the base of the tank.

 

[skjl47]

Hello; Been thinking about your question. Here is another take. Assuming the tank is a rectangle looking down from the top. When a WC is about to be done mark the water level, say with a bit of tape. Drain the water you normally take out. Mark the water level again. If you refill the tank to a higher level use this as the top mark. Being a rectangle and knowing the depth of the water it should be easy to calculate the volume of water changed.

As others have stated the point of a WC is to keep the water parameters within a reasonable range. But while very true that point is a bit aside from the OP's question.

I guess dosing with water conditioners such as PRIME to the total tank volume and not to the actual amount of water changed is a common practice. I have seen it suggested a few times since starting these online fish forums seven years ago. I don't exactly see the point of such overdosing.
Near as I can glean from reading threads the biggest potential problem from overdosing PRIME or SAFE might be a reduction in oxygen levels. Also this appears to be a rare thing, if at all, with PRIME. With SAFE it may be more of a potential problem as the measure of a proper dose can be more difficult.

I do not use water conditioners with a WC because my tap water has only chlorine. I store water in containers a few days. Some have stated I need to use PRIME or the like anyway. However it is my understanding such is not needed. Anyway I have been doing this for decades.

 

[RD.]

I guess dosing with water conditioners such as PRIME to the total tank volume and not to the actual amount of water changed is a common practice. I have seen it suggested a few times since starting these online fish forums seven years ago. I don't exactly see the point of such overdosing.

The point, as explained to me years ago by the CEO and head chemist of Seachem, is to increase the reaction time, which decreases the chance of exposure to chlorine, and/or NH3 (free ammonia) when one is filling directly from the tap.

And it only becomes an overdose if one gets carried away and uses far too much.