Managing water changes with dosing

TimLikesFish · 03/16/2014, 08:34 PM

My tank is at the point where I need to start thinking about automatic dosing. I understand how figuring out dosing amounts work, but how do you manage it with water changes? Most salts have a significantly higher Alk level than we desire in our tanks, so how do you work around that?

mpderksen · 03/16/2014, 09:30 PM

This is a little surprising to me. My water is spot on if I test it prior to adding it. I do the changes on weekends, and test the tank before the changes. If Ca or Alk is low right before, I increase my dosing pumps just a little. The next week, if a little too high, I back them off. I have it pretty dialed in this way. At first I tested both before and after the water changes, but now that I'm in the sweet spot, only before to verify that I'm on target.
My Ca sits at 460, and Alk at 10. This week I'm starting with Mg (after the change) since the test this morning was 1220 according to the Red Sea kit.
I use the rule of frequent testing and small changes at first, the back off once I get a feel for the consumption. If I go on a coral-buying spree, I got back to testing more often for a while. Example, I just refreshed the CUC, so I'm testing Phosphate and the Nitrogen set until I'm sure things didn't get out of whack. Same would be true if I added a poop-machine (AKA a tang).
Is that helpful?

Decadence · 03/16/2014, 10:33 PM

If you're like me, running an ULNS system, it's much harder. Not many salt brands contain 7-7.5 dkh alk when mixed to 1.026sg. All that you can do is lower it with muriatic acid after it had been fully mixed and then allow enough time for the CO2 to dicipate again. Don't do this in the tank.

Reef Frog · 03/17/2014, 02:23 AM

If you're doing a 10% water change with ALK at 12 dkh into a tank at 8 dkh, you will end up with about ALK of about 8.4 dkh - not enough to worry about in most cases.

But if you changed 50% (but you wouldn't do this except in an emergency) in the same scenario, you should end up with about 10 dkh. This might not be good for a tank of sensitive acro corals for example but many other corals wouldn't miss a beat.

If you were really concerned about it, I suppose you could reduce the dosing the day prior to your water change. What do you keep your tank at, and what does the new SW register at?

Decadence · 03/17/2014, 03:05 AM

Quote:

Originally Posted by Reef Frog

If you're doing a 10% water change with ALK at 12 dkh into a tank at 8 dkh, you will end up with about ALK of about 8.4 dkh - not enough to worry about in most cases.

But if you changed 50% (but you wouldn't do this except in an emergency) in the same scenario, you should end up with about 10 dkh. This might not be good for a tank of sensitive acro corals for example but many other corals wouldn't miss a beat.

If you were really concerned about it, I suppose you could reduce the dosing the day prior to your water change. What do you keep your tank at, and what does the new SW register at?

I personally use regular IO salt and when mixed to 1.026sg, the alk usually winds up between 13 and 14dkh, double what I run in the tank. If I don't bring down the alk, I get STNing at the bases of a hand full of my colonies. :-/

TimLikesFish · 03/17/2014, 11:28 AM

I keep my Alk at 8 and Reef Crystals Alk is 13 according to the salt mix chart. My concern is if if have a set amount of Alk dosing everyday, then do a 10% WC bringing my Alk to 8.5, it will never return back to 8 so long as I keep dosing. I am planning to turn my tank to SPS dominated. Will growth alone make up for the Alk difference? I do WC's every two weeks so maybe that's enough new growth to negate the difference? Do most people compensate for it by taking their dosing off line? It just seems like that wouldn't be too stable. Thanks

03/16/2014, 08:34 PM	#1
TimLikesFish Registered Member Join Date: Feb 2013 Location: Long Island Posts: 234	Managing water changes with dosing My tank is at the point where I need to start thinking about automatic dosing. I understand how figuring out dosing amounts work, but how do you manage it with water changes? Most salts have a significantly higher Alk level than we desire in our tanks, so how do you work around that? __________________ Tim

03/16/2014, 10:33 PM	#3
Decadence Registered Member Join Date: Dec 2011 Location: Laurel, MD Posts: 572	If you're like me, running an ULNS system, it's much harder. Not many salt brands contain 7-7.5 dkh alk when mixed to 1.026sg. All that you can do is lower it with muriatic acid after it had been fully mixed and then allow enough time for the CO2 to dicipate again. Don't do this in the tank. __________________ ~Heavily stocked 90 gallon SPS display~

03/17/2014, 11:28 AM	#6
TimLikesFish Registered Member Join Date: Feb 2013 Location: Long Island Posts: 234	I keep my Alk at 8 and Reef Crystals Alk is 13 according to the salt mix chart. My concern is if if have a set amount of Alk dosing everyday, then do a 10% WC bringing my Alk to 8.5, it will never return back to 8 so long as I keep dosing. I am planning to turn my tank to SPS dominated. Will growth alone make up for the Alk difference? I do WC's every two weeks so maybe that's enough new growth to negate the difference? Do most people compensate for it by taking their dosing off line? It just seems like that wouldn't be too stable. Thanks __________________ Tim

03/16/2014, 09:30 PM	#2
mpderksen Registered Member Join Date: Jun 2012 Location: Manteca, CA Posts: 1,853	This is a little surprising to me. My water is spot on if I test it prior to adding it. I do the changes on weekends, and test the tank before the changes. If Ca or Alk is low right before, I increase my dosing pumps just a little. The next week, if a little too high, I back them off. I have it pretty dialed in this way. At first I tested both before and after the water changes, but now that I'm in the sweet spot, only before to verify that I'm on target. My Ca sits at 460, and Alk at 10. This week I'm starting with Mg (after the change) since the test this morning was 1220 according to the Red Sea kit. I use the rule of frequent testing and small changes at first, the back off once I get a feel for the consumption. If I go on a coral-buying spree, I got back to testing more often for a while. Example, I just refreshed the CUC, so I'm testing Phosphate and the Nitrogen set until I'm sure things didn't get out of whack. Same would be true if I added a poop-machine (AKA a tang). Is that helpful?

03/17/2014, 02:23 AM	#4
Reef Frog Registered Member Join Date: Feb 2013 Location: Maryland Posts: 3,121	If you're doing a 10% water change with ALK at 12 dkh into a tank at 8 dkh, you will end up with about ALK of about 8.4 dkh - not enough to worry about in most cases. But if you changed 50% (but you wouldn't do this except in an emergency) in the same scenario, you should end up with about 10 dkh. This might not be good for a tank of sensitive acro corals for example but many other corals wouldn't miss a beat. If you were really concerned about it, I suppose you could reduce the dosing the day prior to your water change. What do you keep your tank at, and what does the new SW register at?