Do you account for displacement for water change?

earlybird

Active Member
29g tank with 29+ lbs. of lr. Doesn't seem to be that much water after displacemt. Is there a formula? I'm just curious. Would 5g water changes weekly be okay for me?
 

lion_crazz

Active Member
Five gallons should be enough. That is a 17% water change on your tank (before thinking about displacement).
However, as the original poster said, the more water changes, the better.
 

mandarin w

Member
You want to account for displacement when figuring how much calcium or buffers, alk, or stuff like that. If you don't remember to account for the displacement it could be disastrous. But for waterchanges, it wont hurt anything.
 

earlybird

Active Member
mandarin,
good to know thanks. Is there a calculation to determine displacement or do you count the gallons when adding water for the first time?
 

hot883

Active Member
I have a 125 gallon. Honestly I never calculated displacement. I change 12 gallons at a time. Why??? Because thats what my rubbermaid container holds. Ha! I have about 300 lbs. of lr and 120-150 of ls.
It's not rocket science. I do not add buffers or calc. etc. those get replaced with my water changes. Barry
 

mandarin w

Member
Well, I don't know if there is a way to calculate it. I guess you count gallons on a smaller tank. I can guarentee you I would have lost count trying that on my 180.

On the larger tanks I guess we just have to take a good guess. and in time you can narrow it down a bit.
 

mandarin w

Member
I wish I didn't need to add for alk, but if I don't my alk/kh stays below 3.6 KH. My tank sucks it up like crazy. Trying to replace just by doing waterchanges just wasn't working. Sometimes you have to add. I don't advocate adding blindly, or adding because anyone else does, or you think that is what you should be doing. I had tanks set up for years and never had any problems, But with my 180, I tried the natural way. and it just didn't work for this system. My system uses it up way to much and way too quickly. So I have to add. Before I add each day, I check what the levels are, then I go to Randy's calculator and enter my levels, then I am told exactly what to add. On a normal day my alk/kh will drop from 3.66/10.2 down to 3.09/8.6, and if I let is go for more than two days it will drop down to
2.29/6.4. And as you know you can not do a water change every day. I am not saying you are wrong, As for beginers they shouldn't be doing this. But they do need to know exactly what is going on in their tank, and how much their tank uses on a daily basis.
 

hot883

Active Member
Originally Posted by mandarin w
I wish I didn't need to add for alk, but if I don't my alk/kh stays below 3.6 KH. My tank sucks it up like crazy. Trying to replace just by doing waterchanges just wasn't working. Sometimes you have to add. I don't advocate adding blindly, or adding because anyone else does, or you think that is what you should be doing. I had tanks set up for years and never had any problems, But with my 180, I tried the natural way. and it just didn't work for this system. My system uses it up way to much and way too quickly. So I have to add. Before I add each day, I check what the levels are, then I go to Randy's calculator and enter my levels, then I am told exactly what to add. On a normal day my alk/kh will drop from 3.66/10.2 down to 3.09/8.6, and if I let is go for more than two days it will drop down to
2.29/6.4. And as you know you can not do a water change every day. I am not saying you are wrong, As for beginers they shouldn't be doing this. But they do need to know exactly what is going on in their tank, and how much their tank uses on a daily basis.
I had problems too and then found out it was my salt. My calcium was super low when I used Instant Ocean. When I switched to Oceanic, problem solved. Salts have different effects with everyones tank. I would try another salt sometime.
 

mandarin w

Member
I used to use Oceanic, but it gave me a very high phosphate problem, You couldn't give me oceanic now.
Now I use a mix of Instant and Coral life.
I just have a lot of corals in my tank that uses the calcium and alk. A lot of SPS, I found that since mixing the two. I am able to keep the numbers higher. When I was just useing one or the other the numbers were harder to get up. But I've never had a problem with my calcium or mag. It has always been my alk/kh that wouldn't want to break a 3.09 for alk.
 

mandarin w

Member
Sorry, Earlybird I didn't mean to steal your thread. I just wanted to explain that sometimes you will need to add something to your tank, like it or not. You will need to account for the water displasment then.
 

earlybird

Active Member
No problem on hitching. I'm soaking it all up. I got the answer I need anyhow. Should be pretty simple to count my gallons when I set up. Thanks
 
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