Confused about water changes

[Reef of Fillory]

Goof afternoon!

I have just started up a Fluval Evo 12 gallon nano in my living room. I have had two reef tanks in the past that I used dosers to maintain ALK/CAL at desired levels and refugium to manage Nitrate/Phosphates with Carbon for the toxins that it can/will filter out.

With that said, I am trying to go on purely weekly water changes with the new tank. I don't want to have to dose for ALK/CAL [If I need to add kalk to ATO I can do that].

I am now looking to buy a salt mix as I haven't done water changes on my previous tanks enough to buy salt [I bought mixed water @ LFS previously when needed].

Since I only have a 12/13.5 gallon tank with maybe 10 gallons total water volume, I am hoping to buy one batch of salt to accomplish no dosing throughout the year [if the salt stays usable this long].

I was looking to buy Reef Crystal salt for the increased dkh assuming that a 10-20% weekly water change would replenish any used ALK/Calcium. I have noticed that the Reef Crystals has a ALK value of 11, and my previous tanks have run at ALKs of 7-8. Should I choose a different salt?

Since I will not be dosing, the water change will be needed to replenish, so I don't think I want to get a salt mix that matches my desired parameters? I would want one that's higher [but 3 points higher?]

Thank you for any input - sorry for the wall of text, i'm thinking as I type.

 

[Reef of Fillory]

Could 10% weekly using Reef Crystals be too much for my 10 gallon tank?

Once demand increases, would an increase in weekly water change % be needed? Wouldn't this cause even greater parameter swings?

I was in the boat/opinion that water changes are not needed most of the time in reef tanks, however I don't want to buy/use a dosing set up on the nano tank. [location makes cords/tubes etc. very visible]

 

[Tedzilla]

Goof afternoon!

I have just started up a Fluval Evo 12 gallon nano in my living room. I have had two reef tanks in the past that I used dosers to maintain ALK/CAL at desired levels and refugium to manage Nitrate/Phosphates with Carbon for the toxins that it can/will filter out.

With that said, I am trying to go on purely weekly water changes with the new tank. I don't want to have to dose for ALK/CAL [If I need to add kalk to ATO I can do that].

I am now looking to buy a salt mix as I haven't done water changes on my previous tanks enough to buy salt [I bought mixed water @ LFS previously when needed].

Since I only have a 12/13.5 gallon tank with maybe 10 gallons total water volume, I am hoping to buy one batch of salt to accomplish no dosing throughout the year [if the salt stays usable this long].

I was looking to buy Reef Crystal salt for the increased dkh assuming that a 10-20% weekly water change would replenish any used ALK/Calcium. I have noticed that the Reef Crystals has a ALK value of 11, and my previous tanks have run at ALKs of 7-8. Should I choose a different salt?

Since I will not be dosing, the water change will be needed to replenish, so I don't think I want to get a salt mix that matches my desired parameters? I would want one that's higher [but 3 points higher?]

Thank you for any input - sorry for the wall of text, i'm thinking as I type.

If the parameters are higher, then that can be a good thing, depending on how many corals you have, and what they are consuming. Remember, when you do a water change, your levels will/should be lower- adding a salt with higher (than your normal) content should bring you to even. Going slightly higher, is better than going lower, in my book. You'll start to see mineral buildups around water edges if it gets too high. I'd maybe go with a combination of Reef Crystals, and the regular salt, so you can switch between the two, until you get a good sense of where you need to be, in conjunction with where each salt puts you at.

 

[Tedzilla]

I know you want to buy one batch, but my experience with sticking to straight water changes... Reef Crystals are a must have.

 

[chipmunkofdoom2]

With that said, I am trying to go on purely weekly water changes with the new tank. I don't want to have to dose for ALK/CAL [If I need to add kalk to ATO I can do that].

Why do you feel that way? In general, water changes are a pretty poor way of elevating magnesium, carbonate and calcium. In a 12g tank, it would take a 25% water change (3 gallons) to raise alkalinity from 7 dKh to 8 dKh (assuming your salt mixes up to 11 dKh). It would take just 8.5mL of BRS soda ash to do the exact same thing. To put it more bluntly, you're dumping 3 gallons of good saltwater down the drain to avoid putting 8mL of liquid in your tank.

To each his own, of course. If you don't want to dose, you don't have to. I've just never understood why people choose to do water changes instead of adding a few mL of liquid to their tanks.

 

[Reef of Fillory]

If the parameters are higher, then that can be a good thing, depending on how many corals you have, and what they are consuming. Remember, when you do a water change, your levels will/should be lower- adding a salt with higher (than your normal) content should bring you to even. Going slightly higher, is better than going lower, in my book. You'll start to see mineral buildups around water edges if it gets too high. I'd maybe go with a combination of Reef Crystals, and the regular salt, so you can switch between the two, until you get a good sense of where you need to be, in conjunction with where each salt puts you at.

One of the things i'm worried about is that if my corals aren't consuming the difference that a 10% water change replaces. I suppose I could just skip a water change or two to keep the levels down into acceptable ranges.

I'm not sure what range of daily ALK demand I should even expect in this small of a tank. If I only need 1 ALK/week, i'd be at around .15 ALK consumption per day. That would require a little more than 10% water change to return to baseline. I'm guessing that throughout the week, my corals might demand higher alk to start, and as the ALK begins to drop, they will consume less of it slowing their consumption rate.

I see some people talking about .5-.75-1 ALK daily requirements, which I can't imagine would be the case in a 10 gallon tank as the DKH would go from 8.5-7.5-6.5-5.5 over 3 days, and things would be dying at 5.5 DKH?

 

[Reef of Fillory]

Why do you feel that way? In general, water changes are a pretty poor way of elevating magnesium, carbonate and calcium. In a 12g tank, it would take a 25% water change (3 gallons) to raise alkalinity from 7 dKh to 8 dKh (assuming your salt mixes up to 11 dKh). It would take just 8.5mL of BRS soda ash to do the exact same thing. To put it more bluntly, you're dumping 3 gallons of good saltwater down the drain to avoid putting 8mL of liquid in your tank.

To each his own, of course. If you don't want to dose, you don't have to. I've just never understood why people choose to do water changes instead of adding a few mL of liquid to their tanks.

Oh I agree with you, on my previous tank I hadn't done a water change in probably 9 months. I don't have the space for dosing lines etc. and want to minimize the required testing and manual dosing to maintain parameters. My last tank was fairly 'set and forget' with the doser. I have read of people more or less accomplishing the same outcome by once a week [or twice a week] water changes.

I suppose if I can dial in a dose, then I could just add the few mL every other day or so but I don't think i'd feel right dosing without testing before/after

 

[Randy Holmes-Farley Verified Community Expert]

I was looking to buy Reef Crystal salt for the increased dkh assuming that a 10-20% weekly water change would replenish any used ALK/Calcium. I have noticed that the Reef Crystals has a ALK value of 11, and my previous tanks have run at ALKs of 7-8. Should I choose a different salt?
.

The limewater is ATO is a good method, but water changes to supplement alk will only work for the very lowest of daily demand, or for massive changes (50% daily).

I show those calculations and graphs here:

Water Changes in Reef Aquaria by Randy Holmes-Farley - Reefkeeping.com
http://reefkeeping.com/issues/2005-10/rhf/index.php

Figure 23. Alkalinity as a function of time when performing very large daily water changes of 0% (no changes), 5%, 10%, 15% and 30% of the total volume EACH DAY. In this example, alkalinity is present at 4 meq/L (11 dKH) at the start and is depleted at a low rate of 0.2 meq/L per day (which is 0.56 dKH per day).

 

[Randy Holmes-Farley Verified Community Expert]

One of the things i'm worried about is that if my corals aren't consuming the difference that a 10% water change replaces. I suppose I could just skip a water change or two to keep the levels down into acceptable ranges.

I'm not sure what range of daily ALK demand I should even expect in this small of a tank. If I only need 1 ALK/week, i'd be at around .15 ALK consumption per day. That would require a little more than 10% water change to return to baseline. I'm guessing that throughout the week, my corals might demand higher alk to start, and as the ALK begins to drop, they will consume less of it slowing their consumption rate.

I see some people talking about .5-.75-1 ALK daily requirements, which I can't imagine would be the case in a 10 gallon tank as the DKH would go from 8.5-7.5-6.5-5.5 over 3 days, and things would be dying at 5.5 DKH?

Why do you think your demand will be so low?

 

[Randy Holmes-Farley Verified Community Expert]

To each his own, of course. If you don't want to dose, you don't have to. I've just never understood why people choose to do water changes instead of adding a few mL of liquid to their tanks.

Me either. It is far, far more expensive to boost alk and calcium by water change, unless the demand is so very low that water changes that you would do for other reasons already cover the need.

 

[Reef of Fillory]

Why do you think your demand will be so low?

I just didn't expect that the growth and stocking of a smaller tank would rival that of the larger tanks I've seen numbers for. I haven't seen much data posted from nano owners, so I just made the assumption. I'm not going to fill it with sps, but I intend it to be a fairly well mixed reef. What range of daily alk consumption do you think I might see on a tank this size? I also know that I have high co2 levels in my apartment and low ph in my tanks, I ran a scrubber on the bigger tank to get my levels above 8.0

 

[Caswal]

My little 60L/15G drops about 1dkh a day. Corals it has zoas, 1 small candy cane, 1 small frogspawn. I assume the alk drop is from the sheer amount of coraline growth my little tank has. I dose and do a 10L water change weekly.

I find making smaller (<10L) amounts you don't get a reliable mix of the salt, and it varies too much when mixed up. Either the salinity isn't as expected or the Ph is off.

 

[Justfebreezeit]

Just kalk in the ato and maintain the Alk at whatever your salt mix is. That way when you do water changes there is no swing.

I have a 20 and my Alk drops about .7 dkh a day and half a teaspoon per gallon in the ato covers it no problem.
I do weekly 15%ish water changes to maintain everything else.

I have a fairly mixed reef.

 

[Randy Holmes-Farley Verified Community Expert]

I just didn't expect that the growth and stocking of a smaller tank would rival that of the larger tanks I've seen numbers for. I haven't seen much data posted from nano owners, so I just made the assumption. I'm not going to fill it with sps, but I intend it to be a fairly well mixed reef. What range of daily alk consumption do you think I might see on a tank this size? I also know that I have high co2 levels in my apartment and low ph in my tanks, I ran a scrubber on the bigger tank to get my levels above 8.0

I don't think tank size is a determining factor in daily alk/calcium demand, except for a small tendency for smaller tanks to use more since they have a higher floor surface area (for corals, etc.) to water ratio.

Demand depends both upon what is growing in the tank and what the pH and alk are maintained at (higher alk and pH mean more demand). A soft coral plus coralline tnak can use 2 dKH per day. Typical values are about 0.4 to 4 dKH per day.