Waterchange. Add water 1st?

[hart24601]

I was curious if there is a general rule of thumb for reduction of efficiency by adding the fresh salt water 1st to the tank then draining the same amount out. I would think the difference would be small, and it's nice to not turn off my ato or make any other changes like turning off return pump, fast and easy to add and remove.


So if I have 30g tank, changing 10% of the water, 3g - what would be the amount I need to change to equal the above if adding the water 1st instead of removong that 3 gallons? If I add 3.3 gallons and remove 3.3 would that be equal for example.

 

[Crabs McJones]

I was curious if there is a general rule of thumb for reduction of efficiency by adding the fresh salt water 1st to the tank then draining the same amount out. I would think the difference would be small, and it's nice to not turn off my ato or make any other changes like turning off return pump, fast and easy to add and remove.


So if I have 30g tank, changing 10% of the water, 3g - what would be the amount I need to change to equal the above if adding the water 1st instead of removong that 3 gallons? If I add 3.3 gallons and remove 3.3 would that be equal for example.

I like to drain the water first then add in your new water. While i'm sure the amount would be minute, if you add your new water first and then drain the water out, you're also draining out some of the new water you just put in.

 

[Martin Kuhn]

+1

Also you would need kind of „reservoir“ within your tank you might not have available

 

[hart24601]

I like to drain the water first then add in your new water. While i'm sure the amount would be minute, if you add your new water first and then drain the water out, you're also draining out some of the new water you just put in.

Exactly. Thats what I am asking. How much more would one need so they are equal hense the would 3.3g adding 1st = 3g or would it be more or less.

 

[hart24601]

+1

Also you would need kind of „reservoir“ within your tank you might not have available

Most sumps are not run at capacity, so it's easy to add the extra water. I have been doing it for years, just am curious how the numbers work out.

 

[Martin Kuhn]

Just very roughly as you would remove again 10% of the 10% added right again ..... add 10% to the 10% you like to change resulting in 3,3 g

Mathematically this might not be not fully correct, but by far accurate enough

The advantage if you do so: you need not lower the water level within your tank temporarily. Anyhow, even if Do no so, this never really stressed my animals

 

[hart24601]

Just very roughly as you would remove again 10% of the 10% added right again ..... add 10% to the 10% you like to change resulting in 3,3 g

Mathematically this might not be not fully correct, but by far accurate enough

The advantage if you do so: you need not lower the water level within your tank temporarily. Anyhow, even if Do no so, this never really stressed my animals

That was my guesstimation, 10% of the 10% but wanted to see for sure. The extra 0.3 gallons is worth it to me as I don't really even measure that close in a 5g bucket, just around the 3-4g range and then take out what I added. Don't have to worry about return sucking in air, unplugging ATO or anything like that. Just makes the chore a little easier not fussing under the stand. Not exactly a big deal but anything that makes it more likely to do W/C and make them fast I am all about. I would also suspect if one didn't want to heat the water 1st the additional volume would buffer the temp change as well.

From a pure number perspective or chemistry perspective is there any reason doing 3.3 (or whatever the exact amount is) would matter at all? It seems somewhat counterintuitive that adding that small additional amount is just as good, but I can't see why it wouldn't be and in some cases couldn't it be thought of as better if you can keep the return running to mix the new and old water more?

 

[KrisReef]

If I add a five gallon bucket that is 6/7th full to my sump, I then remove the same amount of water from my tank, using the same bucket that I fill it back to wherever the water level was in the bucket that I just added so that way I don't have to figure out any complicated ratios.

I do make certain that the fresh mixed seawater I am adding is near the same salinity, temp, kH, pH, etc levels so that I don't shock/stress the animals.

I used to shut the circulation off during changes, drain from the sump and then add back into the sump so that all new water stayed in the tank, but after awhile I quit sweating those details. Water changes are good!

 

[Crabs McJones]

I'm horrible at math so I don't know the numbers, but any amount of the good water getting dumped down the drain would be a waste to me. Trace, minor and major elements down the drain.

 

[hart24601]

If I add a five gallon bucket that is 6/7th full to my sump, I then remove the same amount of water from my tank, using the same bucket that I fill it back to wherever the water level was in the bucket that I just added so that way I don't have to figure out any complicated ratios.

I do make certain that the fresh mixed seawater I am adding is near the same salinity, temp, kH, pH, etc levels so that I don't shock/stress the animals.

I used to shut the circulation off during changes, drain from the sump and then add back into the sump so that all new water stayed in the tank, but after awhile I quit sweating those details. Water changes are good!

Exactly what I am wondering, it's not a big deal, was just curious about how the numbers worked out.

 

[hart24601]

I'm horrible at math so I don't know the numbers, but any amount of the good water getting dumped down the drain would be a waste to me. Trace, minor and major elements down the drain.

Good point. I use reef crystals and the 200g box is generally about 30 cents per gallon. If for my system that extra 0.3 gallons, if that is accurate, the cost of the convenience is 10 cents per water change. The cost of the ro/di wouldn't add enough to bump that another penny.

 

[JBKReef]

Depending on sump overflow volume and any kind of manifolded return you could potentially have zero waste... Granted having to re plumb a system has expense.

I would say if you can turn off return pump, add X gallons to sump, then turn a valve that would divert water from DT to waste water then no issue but that sounds like an overly complicated method if you could just drain the sump first, then add the fresh water into the sump.

 

[hart24601]

Depending on sump overflow volume and any kind of manifolded return you could potentially have zero waste... Granted having to re plumb a system has expense.

I would say if you can turn off return pump, add X gallons to sump, then turn a valve that would divert water from DT to waste water then no issue but that sounds like an overly complicated method if you could just drain the sump first, then add the fresh water into the sump.

That's one of the reasons I am hoping Randy or someone can confirm the numbers, to see if the waste even matters or at least see how much it is. I mean this isn't exactly hobby that is low waste and a few cents here and there isn't going to matter for most people as in my case it appears to be $5 a year.

 

[hart24601]

I was just thinking the math is problem the same as doing automated waterchanges? Since with those you are adding and subtracting at the same time - or at least close to the same. I think can get close with this calculator although you have to play around a bit:

http://angelfish.net/DripSystemcalc.php

On this calculator looks like 3.15g dripped in is 9.97% w/c on a 30g system. Heck that is well within the eyeballing I do on a 5g bucket.

 

[Randy Holmes-Farley Verified Community Expert]

Most people do remove hen add back, but many also do automatic water changes that very slowly do both at the same time. I did that method, changing 1% daily.

 

[vetteguy53081]

 

[hart24601]

Haha. That's why all my FW systems have drips w/c!

 

[MnFish1]

I was curious if there is a general rule of thumb for reduction of efficiency by adding the fresh salt water 1st to the tank then draining the same amount out. I would think the difference would be small, and it's nice to not turn off my ato or make any other changes like turning off return pump, fast and easy to add and remove.


So if I have 30g tank, changing 10% of the water, 3g - what would be the amount I need to change to equal the above if adding the water 1st instead of removong that 3 gallons? If I add 3.3 gallons and remove 3.3 would that be equal for example.

For example: If you add 5 gallons to 10 gallons of water you are leaving the tank with 1/3 new water. (5 gallons/15 total gallons) when you remove 5 gallons.

Instead, If you take the same 10 gallons of water, and remove 5 gallons and add 5 gallons of fresh water - you are leaving the tank with 50 percent ‘new water’.

Over time this can make a significant difference in both cost and water changes. You are basically wasting a portion of the new water (unless you add it to the sump - and remove it from the display). Also depending on the amount of each water change and the frequency. for example if you take 1000 cc out of one end and put 1000 cc new water in the other end- it is probably the same as changing the water directly.

 

[hart24601]

For example: If you add 5 gallons to 10 gallons of water you are leaving the tank with 1/3 new water. (5 gallons/15 total gallons) when you remove 5 gallons.

Instead, If you take the same 10 gallons of water, and remove 5 gallons and add 5 gallons of fresh water - you are leaving the tank with 50 percent ‘new water’.

Over time this can make a significant difference in both cost and water changes. You are basically wasting a portion of the new water (unless you add it to the sump - and remove it from the display). Also depending on the amount of each water change and the frequency. for example if you take 1000 cc out of one end and put 1000 cc new water in the other end- it is probably the same as changing the water directly.

Randy has a good write up on automatic water changes and there are plenty of discussions on monstersfisbkeepers. The larger the single water change the more efficiency is lost, in your emaple a 50% waterchange is pretty big. Every person is wasting water so to speak doing automatic changes too, but how much is the key. In my case it's $5 a year it appears.

I think Randy shows that a 30g w/c is really equivalent of 26g with a continuous system.

How much electricity do we waste for convenience in this hobby or dumping old solutions "to be safe" or obsessively rinsing out things with RO/DI... In the overall hobby this seems like a very small waste unless doing large emergency waterchanges which this post is not about.

http://reefkeeping.com/issues/2005-10/rhf/index.php#13


I just might add the water 1st but dump in the overflow, then most taken from display since it's really fast to do. Or not. It's only a few cents a water change. Still didn't get the math I was hoping for exactly but it seems pretty minimal for 10% amounts to add a bit more. Heck I don't use the bottom of 2 part jugs so can rinse them out and change my ro/di filters before they read 0 so this is about the smallest waste I have. Oh dont get me on foods I have let expire... Embarrassing