ALK - Why do you hate me so?

[davidpesce]

My ALK does not want to stay stable and I'm unsure of what best to do. I'd rather determine the problem rather than just throw chemicals at it.

I noticed my torches looking a little funny about 3 months ago and noticed my ALK was 6dkh. I had been adding more SPS (still very little) and got a recommendation to supplement evap with Kalkwasser. I started a bit faster than I should have and ended up with 10.5dkh within 2 weeks. I toned this down a bit and it leveled out at 8 since then. I figured I was good to go!

I've been measuring dkh daily just to see what's going on and have noticed a steady decline in the last 3 days. I'm down to 7.3 and noticing some of the torches are looking a little angry (tentacles retracted).

Thoughts, ideas, solutions? Any info would be great!

Summary of system:
- 1.5 years old
- 240g total volume (75g DT, 40g DT, 46g fuge - full of macro, 100g sump)
- Weekly water change of 30g
- ATO of RO/DI (4x a day)
- Kalkwasser (1x a day at midnight)
- LED lights on both DTs, PC on fuge
- ASM G3 skimmer
- Salt = reef crystals

Water Parameters
- Ammonia, Nitrite, Nitrate = 0
- Phosphate = .2
- Ca = 560
- Mg = 1500
- pH = 7.9-8.2
- ALK = grrrr
- Temp = 77.9-78.2

 

[der_wille_zur_macht]

I'm sure you've seen this:

http://www.advancedaquarist.com/2002/11/chemistry

It looks like your calcium is a bit high and your alkalinity is a bit low. From that:

If alkalinity were less than 4 meq/L (11 dKH; the most common situation in zone 4; shown in Figure 5), I would advise correcting this problem by adding an alkalinity supplement until you have moved into the target zone (or zone 1). For systems with a pH of 8.2 or above, baking soda (sodium bicarbonate) is a good choice. For systems with a pH below 8.2, washing soda (sodium carbonate) is a good choice (though use some baking soda too if the correction is a large one and the pH gets too high; that is, above pH 8.5 or so).

I'd take a two-pronged approach - correct the problem now, then adjust your longterm plans to keep things in step - consider these two discrete processes. First, Use baked baking soda or washing soda to slowly get your alkalinity in the target range. Stop dosing kalk or anything that may add calcium during this period in order to allow your calcium level to naturally fall into the target range while you're correcting the alkalinity.

Once both parameters are within the target range, revise your approach to maintaining them. Compare your target parameters to the values you get in newly mixed ASW for your water changes. If the new ASW isn't in line with your desired parameters, either correct it (I use two-part and/or kalk to correct newly mixed water as appropriate) or switch brands to something that IS within your desired range. That accounts for water changes. Then, use a balanced method to dose and tune it to keep levels in line. I like kalk, and since you already have a mechanism for that, I'd stick with it. Adjust the volume of kalk dosed nightly to keep the parameters in line. For most tanks, calcium and alkalinity stay in the correct relative proportions when using kalk (or other balanced dosing mechanisms) but once in a while a tank will require small corrections to one or the other. If the correction is small enough, you may be able to make up for it with very occasional dosing of one part or the other from a two-part system. Or even just adjusting the values on your water change ASW.

 

[der_wille_zur_macht]

Also, your magnesium looks a bit high. Are you dosing for it?

Actually, are you dosing anything besides kalkwasser?

 

[davidpesce]

Nate - excellent article, thanks for posting! I've read it in the past, but it's a good refresher and helping me get a better handle on it.

I'm worried that correcting the system, short term, won't address the problem long term. And then I'll get into a dosing nightmare where I'm constantly adding chemicals to balance it out. What would cause my ALK to go low? It seems like the high Ca is causing calcium carbonate precipitate? I've never tested the new saltwater, but assumed since it's the same I've used all along it would be stable at 8.

For the first year I didn't dose anything. Just weekly water changes and everything was fine (Ca around 420 and ALK at 8). Then my ALK dropped and I added KW to hopefully address it. Maybe KW is not what I needed?

Nope, not dosing any mg or anything else, just KW.

 

[teamdulski]

I would check your fresh mixed Reef Crystals, I know of a few people (not on Reef Central) having similar problems that use Reef Crystals and they don't dose anything: high calcium(550-600), low alk, high magnesium(1500-1700) and I have started to wonder if there is a bad batch floating around.

 

[davidpesce]

Adam - This is all starting to make sense... I think between you and Nate you've got it nailed!

I got two boxes of reef crystals about 3 months ago, pretty much when my problems started.

I'll check a fresh mix tonight and see what I find. I may not need to dose anything at all!

 

[der_wille_zur_macht]

It's pretty much like every thing else in reefkeeping - you have to look at your inputs (water changes, dosing) vs. your outputs (water changes, uptake by corals). In general, Calcium and alkalinity are used "in proportion" with each other via uptake by corals, and dosing kalk adds them in the same proportion - so if you're dosing kalk and things are way out of whack, it's probably not the dosing or the coral uptake causing the problem, which pretty much leaves water changes as the culprit.

So, definitely take a look at the water change - but, then, once you know it's no longer causing problems, consider your longterm dosing as a separate issue/process. Indeed you might find you don't need to dose anything if the water change water has correct values, or you may find you need a small kalk dose to keep up. Either way I'm pretty sure you won't need to keep dumping a bunch of chemicals in the tank - barring any major changes (bad salt, different brand of salt, adding a ton of corals, removing a ton of corals), it's usually the case that you can easily work out a set routine and then stick with it for months/years without adjustments or tons of effort, especially in a lower-stocked tank.

 

[davidpesce]

ABC - Always Be Checking... your assumptions!

ABC - Always Be Checking... your assumptions!

It's pretty much like every thing else in reefkeeping - you have to look at your inputs (water changes, dosing) vs. your outputs (water changes, uptake by corals).

Yeah, I completely overlooked this and drew conclusions based on faulty assumptions.

I haven't checked the fresh saltwater mix yet, but it makes logical sense. I was assuming that the salt mix was stable and it had to be something else. Can't wait to go home and test it!

 

[SkiFletch]

I find my tank runs similarly with a higher demand for alk than calc. I do kalkwasser topoffs and correct my input seawater from water changes (which tends to be just a little low) but I still end up with alk sagging faster than calc. My kalkwasser topoff isn't quite enough to boost either variable so I end up supplimenting with 2-part. I'm currently on about a 1.5:1 ratio of dosing alk:calc with the 2-part additions. When the windows open in the spring/fall, my dosing shifts more to even with dosing reccomendations so I have a personal theory that CO2 is playing some sort of wierd nefarious role in the chemistry at hand that I don't quite get.

Also as an aside, I find everything (calc, alk, coral health, algae growth) stays in a much happier balance when I keep Magnesium normal to high. If I slack on Mg testing/dosing and it drops much below 1350, everything starts getting funky. Just my experience

 

[der_wille_zur_macht]

When the windows open in the spring/fall, my dosing shifts more to even with dosing reccomendations so I have a personal theory that CO2 is playing some sort of wierd nefarious role in the chemistry at hand that I don't quite get.

Could it have something to do with differences in evaporation rate?

The important relationship between CO2 and alkalinity is that, together, they essentially determine the pH in your aquarium. CO2 levels can't directly alter alkalinity levels. Look at the "Alkalinity Facts" segment in this article:

http://www.advancedaquarist.com/2002/2/chemistry

If the window being open was changing CO2 levels in the home's atmosphere, you might expect a change in pH in the tank but not a change in alkalinity.

 

[SkiFletch]

Well I notice a change in pH to be sure. Usually runs about 7.9-8.1 winter/summer and 8.1-8.3 spring/fall (AC in summer, heat in winter) but I also notice a difference in alkalinity demand as well. It's not like some rapid crash/change, more of a seasonal variation. Might be evap rate too as dewpoint is definitely variable across those seasonal combinations

 

[der_wille_zur_macht]

Is your kalk dosing fixed, or variable as part of an ATO?

Does temperature in the tank change seasonally?

It could be different growth rates for the organisms in the tank (resulting in faster/slower uptake of alkalinity) in response to different pH or temperature seasonally.

 

[SkiFletch]

Variable, ATO with home-made tronics

Temp varies rather significantly. I allow it cooler in the winter and warmer in the summer as I'm pretty energy conscious. Keeping upper 70's in the winter is much more expensive than low 70s, and around 80 in the summer is cheaper than running the fans constantly to keep it down in the low-mid 70's... So yeah it would make sense that a combo of growth rates of different corals as they respond to pH and temp variations would probably make the most sense. CO2 does still play a role in the pH and thus coral growth rate, and thus alk uptake. I wonder if the OP has similar livestock to me. I've got mostly LPS. Heavy on hammers/frogs/torches along with a bunch of Acans (who doesn't in buffalo...), a couple blastos, handful of palythoa, a crocea clam, along with a superman monti, green poci, and green milli. Oh yeah, and a Favia too.

 

[davidpesce]

I just want to say, I LOVE YOU GUYS!!

Got home and tested a fresh mix of reef crystals salt and got a reading of 5.4 alk. Wish I had found out sooner so that I could complain to the manufacturer.

Anybody know of a way to let others know about that batch?

 

[der_wille_zur_macht]

Go start a thread in the main reef forum, make it factual and thorough, and ask if others have seen a trend.

 

[teamdulski]

I just want to say, I LOVE YOU GUYS!!

Got home and tested a fresh mix of reef crystals salt and got a reading of 5.4 alk. Wish I had found out sooner so that I could complain to the manufacturer.

Anybody know of a way to let others know about that batch?

I will pass this on to a few very happy people that won't think they are crazy anymore. I wish I had the the contact info for that product line rep.