Why do some do water changes and others do not?

[Princess Hockey]

As the title says, I'm wondering why some people do water changes and others do not. What parameters specifically are the regular water changes managing?

It doesn't seem like 20% would lower bad numbers by much in a large system...so are they more about replacing missing nutrients that get taken out of the water? Nutrients that exist inside of the salt mixes? Obviously I don't totally understand it all yet. I haven't done a water change yet on my main tank, well I did a 5% change, mostly because I was stealing so much water to do various other things that I had to make some salt water and put it back.

My tank is about a month old, very light bioload (2 clowns, 10 hermits, 8 snails in ~115g total system volume)

Ammonia - 0
Nitrate - 1ppm
Phosphate - 0.1ppm
Calcium - 480ppm
Alkalinity - 7dKH
Magnesium - 1480ppm
Salinity - 1.025
PH - 7.9
Temp - 79.7-80.1 ish.

I was keeping a close eye on nitrates as I added the fish and started feeding them. Since I wasn't sure how much to feed and they eat like pigs, was worried I was surely overfeeding, but nitrates have never approached 2ppm. I'm sure my parameters aren't perfect, but they don't seem that far off, and everybody seems to be healthy. So if I were to do a water change, what would I be hoping to accomplish?

 

[Dsnakes]

A lot of people do water changes to replace the used elements and not only for nutrient removal. New saltwater adds back in all of the trace elements needed for coral. Sometimes with a high demand, dosing these elements is also needed as the water changes do not replace enough.

Others only dose and do not change the water for the Triton method.

I hope that helps a little bit, I’m not the best at explaining some things

 

[saltyfilmfolks]

Agreed ^

Many avoid water changes because ,
It’s work.

Many do water changes because they think they have to. No other reasoning
As dsnakes mentioned , it replaces trace Elmemnts and minerals for the corals.
So many I find are doing massive 10-20 weekly water changes in a 6 week old tank with one Xenia.
With zero nutrients.

Nitrates are in the water. They do get lower with water changes. You can do massive changes and get it quite low.
Phosphorus binds to rock but comes into equilibrium with the water. So water changes effect Po4 less. Ie , If you did constant or large weekly changes the Po4 would go down. One big one would give little effect.

Many of the older salt mixes came with high alkalinity and high calcium and magnesium as most did as you said , smaller changes, but the the impact on those Elements was greater.
Instant ocean and reef Chrystal’s are good examples of this type of salt.

 

[madweazl]

I only dose two part so the only way to reintroduce the rest is via water change. I don't need them for nutrient removal, I need them for macro and micro-elements. I change 12% weekly and thus far, that has been enough to keep acceptable levels. As things grow out, I assume the need for larger changes will increase but we'll see.

Edit: I use Instant Ocean

 

[Princess Hockey]

When you guys are saying "trace elements and minerals" I assume those are things that I'm not testing for, thus have no idea what levels they're at? And I'm putting them back in with salt?

 

[saltyfilmfolks]

Calcium alk and magnesium are the most common when we refer to minerals.
But yes , most others are not tested for commonly.

 

[WVNed]

Have you ever read a thread about an ICP test? All that stuff.

Water changes are a sledgehammer way to make sure they stay somewhat close to where they need to be. A water change takes the some of the bad stuff out and puts some of the good stuff back.

 

[madweazl]

When you guys are saying "trace elements and minerals" I assume those are things that I'm not testing for, thus have no idea what levels they're at? And I'm putting them back in with salt?

Unless you're adding them via some type of balling method (something like Triton, AquaForest, etc.), that is typically the only way they're reintroduced (i.e. water changes). How relevant they are is another can of worms but I figure if they're in the ocean the critters adapted too, I may as well keep it as close as I can.

 

[vetteguy53081]

I do water changes twice per year. I use triton in my main tank and all my maintenance requirements are at my sump and I lose 3-5 gallons weekly from evaporation so in essence, water is exchanged/ graded weekly.

 

[madweazl]

I do water changes twice per year. I use triton in my main tank and all my maintenance requirements are at my sump and I lose 3-5 gallons weekly from evaporation so in essence, water is exchanged/ graded weekly.

Water with nothing in it is exchanged, which, leads to a net of nothing.

 

[vetteguy53081]

Water with nothing in it is exchanged, which, leads to a net of nothing.

Exchanged meaning replenished and of coursed tested at least monthly to assure parameters are maintained. And the water added does have PO4 reducer, potassium and iodine so not quite a net of nothing. This is result:

 

[madweazl]

In addition to Triton supplements, you're adding something to reduced phosphates, increase potassium, and iodine in your top off water:?

 

[vetteguy53081]

In addition to Triton supplements, you're adding something to reduced phosphates, increase potassium, and iodine in your top off water:?

yes as I have over 35 fish and based on ICP-test, I lack those elements slightly

 

[chipmunkofdoom2]

When you guys are saying "trace elements and minerals" I assume those are things that I'm not testing for, thus have no idea what levels they're at? And I'm putting them back in with salt?

This is the idea. You mentioned however that 20% wouldn't lower bad numbers by much in your original post. The inverse is true for things we want to add. Water changes seem to be adequate in terms of supplementing elements in our tanks, but they're certainly not efficient. The change in any given parameter can be defined as the following:

D = Pwc x Diff

D = delta, or change
Pwc = % of water change in decimal (25% = 0.25)
Diff = the difference in the element between the new water and your tank. Basically, concentration in water change minus concentration in tank

Say your tank has 400 ppm calcium and your salt mix has 450 ppm calcium. You do a 20% water change. The difference = 0.20 * (450 - 400) = 10 ppm. So in a 115 gallon tank like yours, dumping 23 gallons of seawater down the drain would only get you a net increase of about 10 ppm calcium (if your tank and new water are as above). Not the most efficient.

The math seems even more silly when you discuss elements present in smaller quantities. Take boron, which is present at about 4.5 ppm in seawater. Say your tank is severely depleted of boron and only has about 2 ppm. You want to raise boron for buffering (or other) reasons. Assuming your salt mix has natural values of boron, a 20% water change will only raise boron by 0.5 ppm (0.20 * (4.5 - 2)). Not very efficient, especially when a 20% change in a tank your size is 23 gallons.

I don't mean to say there is a good alternative for handling trace elements. As you mention, without testing for these, it's sort of a guessing game in terms of supplementing them directly. Plus, in many tanks, water changes seem to be enough despite the fact that partial water changes will only ever return a small portion of the elements, trace or otherwise. However, I don't think it can be said that water changes are efficient means of supplementing elements. They are likely good enough though.

 

[madweazl]

This is the idea. You mentioned however that 20% wouldn't lower bad numbers by much in your original post. The inverse is true for things we want to add. Water changes seem to be adequate in terms of supplementing elements in our tanks, but they're certainly not efficient. The change in any given parameter can be defined as the following:

D = Pwc x Diff

D = delta, or change
Pwc = % of water change in decimal (25% = 0.25)
Diff = the difference in the element between the new water and your tank. Basically, concentration in water change minus concentration in tank

Say your tank has 400 ppm calcium and your salt mix has 450 ppm calcium. You do a 20% water change. The difference = 0.20 * (450 - 400) = 10 ppm. So in a 115 gallon tank like yours, dumping 23 gallons of seawater down the drain would only get you a net increase of about 10 ppm calcium (if your tank and new water are as above). Not the most efficient.

The math seems even more silly when you discuss elements present in smaller quantities. Take boron, which is present at about 4.5 ppm in seawater. Say your tank is severely depleted of boron and only has about 2 ppm. You want to raise boron for buffering (or other) reasons. Assuming your salt mix has natural values of boron, a 20% water change will only raise boron by 0.5 ppm (0.20 * (4.5 - 2)). Not very efficient, especially when a 20% change in a tank your size is 23 gallons.

I don't mean to say there is a good alternative for handling trace elements. As you mention, without testing for these, it's sort of a guessing game in terms of supplementing them directly. Plus, in many tanks, water changes seem to be enough despite the fact that partial water changes will only ever return a small portion of the elements, trace or otherwise. However, I don't think it can be said that water changes are efficient means of supplementing elements. They are likely good enough though.

This assumes depletion rates are equivalent across the board; I'm not sure if that is true or not. 20% may be more than enough for some micro/trace elements. Having completed four or five ICPs, it wasn't enough in the case of iodine initially but I'd be curious to see the next results. Of course, I'm not really sure iodine (or many others) has any real benefit either. There is a lot ambiguity with all we do.

 

[chipmunkofdoom2]

This assumes depletion rates are equivalent across the board; I'm not sure if that is true or not. 20% may be more than enough for some micro/trace elements. Having completed four or five ICPs, it wasn't enough in the case of iodine initially but I'd be curious to see the next results. Of course, I'm not really sure iodine (or many others) has any real benefit either. There is a lot ambiguity with all we do.

The math doesn't really assume anything and it isn't dependent upon the consumption rates. All the equation states is that the increase (or decrease) of a water change is simply the % of the change times the difference between new water and tank water. It's more useful as a framework of thinking about concentrations than it is doing raw calculations. The equation really means that it takes a lot of water to make relatively small changes, and the effectiveness of the change goes down the closer your values are to normal.

If your point was that elements with almost no consumption will be kept in line with water changes, that's true. But, if these elements really almost have no consumption, you could probably lengthen your water change interval and still not see any significant decrease in the elements. The effect of water changes on all elements in our tanks is pretty small. The effect is even smaller the closer you are to the values in your salt mix.

 

[Centerline]

Water changes also help remove the toxins that many corals produce in an effort to mark their territory. It's basically biological warfair in a tank packed with corals. It's always been interesting to me to watch corals perk up after a water change. That said it's obvious that no change methods work. I have a buddy that hasn't done a water change in a couple of years and his tank looks great. Ca/alk/mag, Purigen, N0POX and the Redsea colors program is all he does.

 

[madweazl]

The math doesn't really assume anything and it isn't dependent upon the consumption rates. All the equation states is that the increase (or decrease) of a water change is simply the % of the change times the difference between new water and tank water. It's more useful as a framework of thinking about concentrations than it is doing raw calculations. The equation really means that it takes a lot of water to make relatively small changes, and the effectiveness of the change goes down the closer your values are to normal.

If your point was that elements with almost no consumption will be kept in line with water changes, that's true. But, if these elements really almost have no consumption, you could probably lengthen your water change interval and still not see any significant decrease in the elements. The effect of water changes on all elements in our tanks is pretty small. The effect is even smaller the closer you are to the values in your salt mix.

I don't disagree with that, perhaps efficiency though. Triton (for instance) hasnt proven to be more cost effective than water changes; I haven't played with any of the balling methods so I don't know if one is more efficient than the other.

 

[Bpb]

Every tank is so different. Large water changes work wonders for rapidly removing something you don’t want. Small water changes are good at removing some elements and boosting others, provided the amount of water removed and replaced exceeds what you’re trying to add or remove as far as it’s rare of buildup or depletion. If that makes sense.

It’s been said. People will rationalize it all day long, but at the end of the day, the only reason people don’t do them is the perceived cost and effort involved. To the point people often spend MORE money and time on products to replace water changes. Baffles me. I digress.

I’ll tell you why I do them. Because when I don’t, my tank is less happy. I can verify that 10-15% every week or two is optimal for my bioload. If I push past the 4-6 week mark without a water change I start getting angry acropora. Tank has been running enough years for me to settle on that conclusion. I imagine it’s a trace element thing for me

 

[Princess Hockey]

I don't disagree with that, perhaps efficiency though. Triton (for instance) hasnt proven to be more cost effective than water changes; I haven't played with any of the balling methods so I don't know if one is more efficient than the other.

Triton method requires a refugium right? I think that's why I haven't looked into that one, not really good space in my sump (red sea s-400) for one. Thinking about an algae scrubber though.

It really seems like I should be focused more on dosing, or at least spending more time reading up on how to do it. Learned from my local coral seller that my alkalinity was low and I should bring it up. So a quick small water change brought me up 0.3 and a conservative (I was being cautious) dose of baking soda brought me up another 0.4 or so. Waiting another day to bring it up any further.


This thread has been very helpful in understanding exactly what is going on. I need to figure out how to more efficiently water change than I've been attempting.