How am I supposed to moderate dosing?

[Phyber]

For the last two weeks, I was testing my alk with a Salifert kit and getting consistent .04 dkh daily drops. Maybe a day here or there was only .02 but mainly .04

I started manually dosing BRS 2 part. The calculator says for my 65g volume to add 18ml daily for that drop, however I was doing my best to dose 15 ml so I am cautious. I've been adding that much this week, but when I tested tonight it had risen from the 9.6 I'm holding to 10.4.

I have a dosing pump on the way, and assuming I let this continue with a daily 15 ml dose, that could be bad! Why would this happen? What can I do against it....just dose less of each of alk and Cal?

 

[SteveEreef]

For a .28 dKH change a week I personally wouldn’t bother dosing. I would just do weekly water changes unless you have Acros that are super sensitive.

 

[JimWelsh]

One approach would be to get a better average daily consumption value by taking a reading several hours after the last dose or water changes, then stopping any dosing or water changes for a few days, and taking another reading after the few days, and then getting an average over those few days, and basing your dosing conservatively on that average. It's easier to measure a larger change and take the average, which will result in a more accurate average, than to accurately see the smaller daily change.

 

[lapin]

Calcium looked ok between the 14th and 18th. So what ever you were doing was working. I would not dose that part unless it drops below 450.
Alk spike from over dosing can be fixed by letting it drop naturally. When back down to your target level I would dose 1/4 of what you were dosing. Test it for a few days then dose again........repeat and if needed up the dose a little more.

 

[Phyber]

For a .28 dKH change a week I personally wouldn’t bother dosing. I would just do weekly water changes unless you have Acros that are super sensitive.

It's a .4 daily drop. I had been doing biweekly 20g water changes, but my schedule is too tight to do more.They also cause big chemistry changes as I can't get the pH up high enough, quick enough, in that amount of water (well water rodi). I do have sps

 

[Phyber]

One approach would be to get a better average daily consumption value by taking a reading several hours after the last dose or water changes, then stopping any dosing or water changes for a few days, and taking another reading after the few days, and then getting an average over those few days, and basing your dosing conservatively on that average. It's easier to measure a larger change and take the average, which will result in a more accurate average, than to accurately see the smaller daily change.

Before I started manually dosing I saw a 1.0 drop over a week. The .4 drops were accurate following the next few daily tests I did...I can try holding off dosing for a few days but I'm looking for stability and automation which is my concern when I start using my dosing pumps

 

[Dkeller_nc]

For the last two weeks, I was testing my alk with a Salifert kit and getting consistent .04 dkh daily drops. Maybe a day here or there was only .02 but mainly .04

I started manually dosing BRS 2 part. The calculator says for my 65g volume to add 18ml daily for that drop, however I was doing my best to dose 15 ml so I am cautious. I've been adding that much this week, but when I tested tonight it had risen from the 9.6 I'm holding to 10.4.

I have a dosing pump on the way, and assuming I let this continue with a daily 15 ml dose, that could be bad! Why would this happen? What can I do against it....just dose less of each of alk and Cal?

There are several sources of potential error when using estimated tank volume/2-part concentration to dose. Most tanks with a nominal volume don't actually have that volume, and it's usually somewhat less. Part of the reason for this is the hobbyist's additions of rock, sand, and equipment. Part of the reason is that tank volume is usually quoted as a volumetric calculation from the interior dimensions of the tank. Since one doesn't run the tank filled to the brim, the actual volume will be somewhat less than what's quoted.

And the BRS calculators (based off of Randy's 2-part recipes) are useful for a starting point to make sure that you're not wildly off, but they weren't meant to be absolutes. The intention is to do exactly what you've been doing - generate accurate test results and adjust the dosing accordingly.

 

[Randy Holmes-Farley]

It's a .4 daily drop. I had been doing biweekly 20g water changes, but my schedule is too tight to do more.They also cause big chemistry changes as I can't get the pH up high enough, quick enough, in that amount of water (well water rodi). I do have sps

I was about to post that you calculated wrong, but since you upped the daily drop from 0.04 to 0.4 dKH, the amount added is appropriate. I agree with others to track longer than 1 day. The errors in a single day of monitoring are too high to set your dosing schedule.

pH is not important during a water change, as long as the final pH is nit lower than about 7.8.

 

[Phyber]

I was about to post that you calculated wrong, but since you upped the daily drop from 0.04 to 0.4 dKH, the amount added is appropriate. I agree with others to track longer than 1 day. The errors in a single day of monitoring are too high to set your dosing schedule.

pH is not important during a water change, as long as the final pH is nit lower than about 7.8.

Thanks Randy, seems like it was too many decimal places along with wine when posting

So, I need to start using a week long dkh drop level vs repeated daily averages? When I did that prior, it was a 1.0dkh drop over a week, which averages a .14 drop daily. Is that what I should shoot for with my dosing schedule?

It seemed my daily dosing was holding good with alk, then I let it go a few days while dosing without testing and it shot up. Cal and mag held steady.

 

[Phyber]

There are several sources of potential error when using estimated tank volume/2-part concentration to dose. Most tanks with a nominal volume don't actually have that volume, and it's usually somewhat less. Part of the reason for this is the hobbyist's additions of rock, sand, and equipment. Part of the reason is that tank volume is usually quoted as a volumetric calculation from the interior dimensions of the tank. Since one doesn't run the tank filled to the brim, the actual volume will be somewhat less than what's quoted.

And the BRS calculators (based off of Randy's 2-part recipes) are useful for a starting point to make sure that you're not wildly off, but they weren't meant to be absolutes. The intention is to do exactly what you've been doing - generate accurate test results and adjust the dosing accordingly.

I figured with some dosing tests that 65g volume is about spot on for my system. The BRS calculator had me on point with their suggestion on the first try, which is why I was intending to base my amounts on that.

But is this something I'm going to have to monitor frequently? Rise and fall of alk usages? I'm wanting to stay consistent and stable with my dosing pumps and system.

 

[Randy Holmes-Farley]

there’s no perfect way to do it because the drop depends on the absolute alk level. I’d go by trial and error, dosing 0.15 dKH per day and adjust the dose after a few days.

 

[Dkeller_nc]

But is this something I'm going to have to monitor frequently?

Generally speaking, yes. But opinions vary on how often to test. Those with soft corals and less sensitive LPS tend to test alk less often, those with SPS, especially acropora, tend to test more often. It's something you could ask specifically on the SPS forum to get a range of opinions, and my guess is that once every 3 days would be about average.

In my case, I test at least once a week when the corals (mostly acropora and montipora) in my tanks are growing at a steady pace. If I take out a fair amount of coral, I may test once every 2 days for a while to re-set my dosing levels and to verify that the alk level has stabilized.