What are water changes for?

[Sk8r]

Two things:
a) they lower nitrate just by getting some of the crud out, as fresh water dilutes the crud that's left.
b) it removes depleted water (which has had some of its trace elements used up) with new water with a fresh dose of trace elements. If you ever look at how you supplement some traces, it's bizarrely crazy, because the dosage is less than a drop for 50 gallons. How do you get 'less than a drop' of something or dose a 30 gallon tank? ask a science lab.

To avoid that crazy-making and basically inaccurate mess of 'less than a drop' supplements you just do your water changes with a salt mix that has the right trace elements in it.

Can you 'come from behind' and catch up if, say, life happens and you're way behind and your tank's an embarrassment? Sure. No time like the present. Start mixing. You can do a 30% water change for starters, wait a couple of days and do a 20% wait another couple of days and do yet a second 20%. Give it a rest, let the bacteria catch up, and then in about a week, start it all again.

YOu'll find everything appreciates it.


Also, if some element (magnesium comes to mind, of personal experience) is just getting extravagantly over-supplied, change salt brands. If you don't have a very packed reef sucking it up, your brand may be not be the best for you. I found that Oceanic is quite rich in mg, and Instant Ocean much lower: for a beginning reef it may be better, and then as your corals increase, you might want to change again, because a trace element that isn't being used up just isn't helping you and might get excessive.

 

[C.Eymann]

Two things:
a) they lower nitrate just by getting some of the crud out, as fresh water dilutes the crud that's left.
b) it removes depleted water (which has had some of its trace elements used up) with new water with a fresh dose of trace elements. If you ever look at how you supplement some traces, it's bizarrely crazy, because the dosage is less than a drop for 50 gallons. How do you get 'less than a drop' of something or dose a 30 gallon tank? ask a science lab.

To avoid that crazy-making and basically inaccurate mess of 'less than a drop' supplements you just do your water changes with a salt mix that has the right trace elements in it.

Can you 'come from behind' and catch up if, say, life happens and you're way behind and your tank's an embarrassment? Sure. No time like the present. Start mixing. You can do a 30% water change for starters, wait a couple of days and do a 20% wait another couple of days and do yet a second 20%. Give it a rest, let the bacteria catch up, and then in about a week, start it all again.

YOu'll find everything appreciates it.


Also, if some element (magnesium comes to mind, of personal experience) is just getting extravagantly over-supplied, change salt brands. If you don't have a very packed reef sucking it up, your brand may be not be the best for you. I found that Oceanic is quite rich in mg, and Instant Ocean much lower: for a beginning reef it may be better, and then as your corals increase, you might want to change again, because a trace element that isn't being used up just isn't helping you and might get excessive.

+1. However dosing less than a drop would be fairly easy mix drop into 10ml of tank water and add % you need back into the tank.

 

[Sk8r]

If you really want to be that fiddly. Yep. It can be done. But then you have all these dilution jugs sitting about...

I actually did that once, because as a crazed novice, I 'heard that x is a key to colorful corals' ---which it really isn't, and you can trash your tank with a mistake. But I tried it. Well, mm, you leave a lid off. Evaporation increases the concentration, etc, etc. The word PITA embroidered in flaming red, sfaic!

And if you look at the NUMBER of traces delivered by your salt mix, it's a LOT.

Hobbyists really have done it both ways, and I'm sure the Atlanta Aquarium actually does dose specifics (big tanks forgive little errors). But the hobby has settled on the one anybody can do (math skills not highly required) and recommended a procedure that will work out as well as the one with a lot of test kits, bottles, measures and jugs.

 

[snesbit01]

is there such a thing as too large of a water change? i see lots of people doing 10% to 30% water changes. i typically do about 50% water changes every week or two. am i doing any harm to my tank changing that much water at a time?

 

[Sk8r]

Depends on what you have in your tank: in a fish-only with filtration it might be beneficial. WIth more fragile corals in a well-established reef, probably not so much. 30% at a go is usually enough even for large changes---but in an emergency, with, say, a problem in the tank, 'dilution is the cure for pollution.'

 

[snesbit01]

Ok. Right now I only have one clown, a cleaner shrimp and 5 hermits. No coral as of yet. So should I reduce my water changes to 30% or is the 50% ok to keep doing?

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[Sk8r]

SHouldn't hurt much, but 30% is enough.

 

[CStrickland]

is there such a thing as too large of a water change? i see lots of people doing 10% to 30% water changes. i typically do about 50% water changes every week or two. am i doing any harm to my tank changing that much water at a time?

If you need to do 50% change every week there's something wrong. It doesn't sound like you're hurting anything besides your wallet, and maybe your back from schlepping all that water. But it's a big waste of energy, time, money, and water IMO. Also, you need to match parameters carefully when you swap out that much water, so there's some risk you'll screw up in a way that isn't there for a smaller change. Like, I can do a 10% change without heating the water and my tank doesn't notice. If I did that with 50% I think death would follow.

 

[MikeyAl]

Great write up


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[MikeyAl]

Ok. Right now I only have one clown, a cleaner shrimp and 5 hermits. No coral as of yet. So should I reduce my water changes to 30% or is the 50% ok to keep doing?

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Why not just do 5-10% each week? Depending on you tank size, 30% can be a lot of hard work. Keep it simple. I have a 90 gal and do 5% each week. Simple 5 gallon. Easy and not a big mess. No lugging large volumes up and down my stairs.


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[Protoavis]

From a math perspective, if water changes are to replenish depleted trace elements, unless the salt mix has higher than "normal" levels of those trace elements over time the tank would be lower than "normal".

I mean say you do 10% weekly changes, if you're tank uses 12% of X trace a week your tank will be below "normal" which would be compounding that decline weekly.

Having said that, we don't have accurate testing for a lot of trace elements so it's a bit "do whatever works for you, mileage may vary"

 

[Sk8r]

THis is true. And eventually things get out of balance.
For example, a tank with stony coral or clams uses calcium like mad, and also consumes quite a bit of magnesium compared to a fish-only or softie tank. Reef salt has quite a bit of all these---plus, I suspect, additional buffer. And reef salts themselves differ: Oceanic has quite high magnesium, which is great if you have a really 'stuffed' reef, while it may be too much for somebody just starting with corals: Instant Ocean has less.

OTOH, the situation you name is part of what we call 'old tank syndrome', in which things aren't great for reasons you can't put your finger on.
This is when a program of closely connected water changes can help. You check your lights for expiration, and your refractometer to be sure that's calibrated correctly, and then you start in with the 30-20-20 water change pattern. 30 one day, 20 two days on, 20 two days after that. Give it a week and do it again, to a total of about 4x. Or more if you have the funds. Very often this will perk up the ailing tank considerably.

 

[MikeyAl]

From a math perspective, if water changes are to replenish depleted trace elements, unless the salt mix has higher than "normal" levels of those trace elements over time the tank would be lower than "normal".

I mean say you do 10% weekly changes, if you're tank uses 12% of X trace a week your tank will be below "normal" which would be compounding that decline weekly.

Having said that, we don't have accurate testing for a lot of trace elements so it's a bit "do whatever works for you, mileage may vary"

Good point. And I do add reef fusion 1+2 and trace elements every wed along with the small water changes weekly. And I do test weekly as well.


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[Sk8r]

On the other hand, frequently adding elements in amounts which may not be used can also pile up in the tank. It's a pretty good maxim: 'don't dose what you don't have a test for'. Be sure what's in the supplements and do take a look at your brand of salt mix to see how they may mesh. Adding magnesium to a tank with few corals while using Oceanic Reef Salt, eg, could create a problem.

Essentially, what goes into the tank stays there and does NOT leave. It can't evaporate unless it's water; and does not go away except by a) being eaten [even so a certain amount may be poo'ed back in, especially so with phosphate]---and except through water changes that have less of whatever-it-is than the water does.

 

[snesbit01]

well i finally got my red sea test kit and tested for Ca alk and Mg for the first time. my Mg was at 1480 ppm, alk at 12 dkh and Ca at 500ppm. could the large water changes be the reason all the readings are so high?

 

[C.Eymann]

Those numbers are close to RSCP salt, guessing that's what you are using?

 

[snesbit01]

yes. thats what ive been using. should i use a different salt since i dont have any coral yet or just not worry about it?

 

[Sk8r]

As long as it stays at that level I wouldn't worry too much. They aren't bad readings. But do monitor those levels periodically to be sure it's not getting above those figures. If so, time for a brand change. I like them to ride at about 8.3 for alk. I once pushed my alk (I believed an expired test) up off the charts, while using kalk (calcium) in the topoff, and ended up with calcium carbonate deposits (white chalk) in my hoses, valves, pump---it was a royal mess. Some hoses I replaced. Soaked pumps in white vinegar, which cleans it off. And nothing died, but nothing was too happy either. There IS a point beyond which not, and I assure you, with every other hobbyist, I've found it now and again.

 

[snesbit01]

Ok. Thanks for the reply. I will keep checking the levels. After reading all of this I'm probably cut my water changes back to 30% or less.

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