$200 to spare--kalk stirrer or 2 part w/ dosing pumps?

[Stu]

I have about $200 to spare for a tank addition, and I'd like to add either a 2 part dosing system with peristaltic dosing pumps or a kalk stirrer (probably a GSA). Which should I go for?

[Coral Hind]

I vote kalk stirrer and in the long run I think that would be cheaper.

[Ryan S]

2 part dosing and pumps all the way. easier, cheaper, and safer!

[rocko918]

stirrer.

[epleeds]

2 for the stirrer and 1 for 2 part. can we get an explanation why people are suggesting one over the other

[Brian Ward]

The peristaltic pumps w/ 2-part will accommodate your needs much longer than simply a kalk stirrer. Eventually your Ca use will (probably) overtake your ability to keep up with Kalk alone and you will need to add a Ca reactor. Many people are also terrified of kalk overdoses. They do happen, especially with automation and if you put too much kalk in the stirrer (you would do this to avoid having to perform maintenance, refilling the stirrer). However, kalk is an excellent supplement for your tank. It boosts your pH, binds to phosphate causing it to precipitate out, and I believe there are other benefits. This is one of those areas like skimmers - everyone has something they swear by. Both methods will work. There is an earlier very lengthy discussion of 2-part vs. kalk & Ca reactors. I'd read through that as well as look for some articles by RHF over on RC.

[Ryan S]

Good post Brian. I've been working on an excel sheet comparing the costs of 2 part vs. kalk/ca over the short term and long term. I will post it when I get home tonight.

[pco1988]

Stirrer!

[Origami]

How big is the tank?

[DonP]

I have a stirrer and went to dosing about 1.5 months ago. I find that my tank parameters are more stable for my setup. That being the case.....I have a 1 year old GSA stirrer I will give you a good deal on if you are interested.

[Stu]

How big is the tank?

 

It's a 30 gallon.

[Origami]

Honestly, I'd go with the pumps then. It's a small system and the cost recovery time is going to be long with a stirrer.

[Stu]

Honestly, I'd go with the pumps then. It's a small system and the cost recovery time is going to be long with a stirrer.

 

I actually already had a DIY stirrer similar to a GEO that I bought from another WAMAS member last year. I used it successfully for about 3 months. The acrylic top plate popped off when I was moving it out from under the stand to clean it. I don't want to repair it, as it is really big and I worry about the overall construction and the same thing happening again.

 

That said, I already have a decent amount of kalk. Is that what you meant by cost recovery time?

[Origami]

I actually already had a DIY stirrer similar to a GEO that I bought from another WAMAS member last year. I used it successfully for about 3 months. The acrylic top plate popped off when I was moving it out from under the stand to clean it. I don't want to repair it, as it is really big and I worry about the overall construction and the same thing happening again.

 

That said, I already have a decent amount of kalk. Is that what you meant by cost recovery time?

 

Kalk is an inexpensive product if you use a bulk source. The equipment can be somewhat expensive, so the cost of entry can be higher. However, this is mitigated by the fact that you have hardware already (though it's in need of repair). Depending upon the method of dosing and equipment selected, the delivery means for 2-part is often cheaper.

 

Two-part solutions can be more expensive ion-for-ion than kalk, if you're acquiring higher purity stuff. For larger systems with high consumption, this can be more expensive to run.

 

 

Cost_of_ownership = acquisition_cost + operating_cost + disposal_cost - resale_value

 

Assuming disposal_cost = 0 and setting resale_value = 0.5*acquisition_cost (if new), you get

 

Cost_of_ownership = 0.5 acquisition_cost + operating_cost

 

There's an cost equation like this for each option. Both are lines since the first term is a constant and the second actually factors in time. If you were to plot both on a graph, the lines would, in all likelihood, intersect. That point where they intersect is the point at which one option, which started out being the cheaper option, becomes the more expensive option. The point at which this happens is actually what I'm calling the cost-recovery time. In the end, you never really *recover* the cost as, in the end, money's always going in and none is coming out. But one option does become the cheaper of the two.

 

For small tanks, because the demand is often rather low compared to a larger system, it takes longer for the operating costs (or savings) to build up and to offset the difference in acquisition cost.

 

There are other factors to consider:

 

If using a stirrer, you're kalk dosing is limited to the amount of evaporation your system experiences per day since you're probably using an ATO to deliver the kalkwasser. If you have low evaporation, this limits how much calcium and alkalinity is delivered to your system. With two-part, the reliance on evaporation is removed and you can dose what you need, when you need it. Kalk also helps to maintain high pH and also precipitates out phosphates and heavy metals and other undesirable stuff from the water column. On the downside, you need to plan and manage the risk of overdosing. The downside of two-part includes long term salinity creep and the lack of some of the benefits of kalkwasser. Salinity creep can be managed with regular water changes.

 

The bottom line is this: Kalk is great stuff. But, if using life-cycle cost as the deciding factor, small systems are probably better served by two-part and larger systems by other means. This is not a new conclusion, but has been published in other, available online articles.

 

Personally, I'd like to see somebody here set up a system using the Balling method with reduced water changes and targeted ion replacement. A basic two-part system more closely migrates to this kind of a setup than kalk, reusing the investment.

[Coral Hind]

Here is an article that explains the Balling method Tom mentioned above.

[bshriver]

Good post Brian. I've been working on an excel sheet comparing the costs of 2 part vs. kalk/ca over the short term and long term. I will post it when I get home tonight.

I believe Randy Holmes Farley has already done that. I'd have to search for the link though. Kalk/CA reactor wins out in the long run for cost, but it takes a while.

 

For a 30 gallon tank I would go with the pumps/two part. That is what I do on a 46 bow.

 

On larger SPS/clam tanks, go with kalk and ca reactor. You will get the money back over time. That is what I run on my large SPS tank.

Edited February 12, 2010 by bshriver

[Stu]

One thing I like about kalk is that it keeps the ph up. Will 2 part do the same thing?

[bshriver]

Here is the article comparing the costs of all of the ways to add calcium and alkalinity

 

http://www.advancedaquarist.com/issues/feb2003/chem.htm

[bshriver]

One thing I like about kalk is that it keeps the ph up. Will 2 part do the same thing?

 

Yes, but you need to use soda ash not baking soda for the alkalinity part. You can make soda ash from baking soda by baking it in the oven for a few hours. It is not as good at raising pH as kalk though, but it will raise it.

 

There is nothing to stop you from using Kalk for ATO and two part. Just monitor pH closely and make sure you prevent overdosing of the kalk.

Edited February 12, 2010 by bshriver

[bshriver]

One more thing. I dose my 46 gallon with a slurry of kalk every morning when the pH is low. I mix 1//8 teaspoon in a pint of RODI and poor it in the sump. This is Anthony Calfo's slurry method for dosing Kalk. You have to be very careful not to overdose it and make sure that you don't rais the pH more than .2 when you do this.

 

I satisfy the rest of the demand for CA and AlK in that tank with Randy's two part.

[Origami]

Stu, you might find this thread entertaining: http://www.wamas.org/forums/index.php?showtopic=30847

[OldReefer]

I am using 2 part for the first time after years of CA reactors and Kalk. I have never had such control and stability. I adjust the timing so my pH swings are down to .1 or less overnight. I just went away for 3 weeks and it held my alk within .2 dkh. I also do not have to worry about an overdose.

[F&Fmgr]

if you go the two part method, and you want an alk boost but your ph is alreay high...you can mix 8 tsp bicarb to 1 ts carb and the carb should netralize much of the dissolved CO2---per the guys at BRS

 

Sean

[Ryan S]

Here is the article comparing the costs of all of the ways to add calcium and alkalinity

 

http://www.advancedaquarist.com/issues/feb2003/chem.htm

 

While this article still has some good information, the cost comparison section is very outdated. It's also pre-BRS and their cheap 2 part system.

[Ryan S]

http://www.wamas.org/forums/topic/35413-brs-2-part-cost-analysis/

 

Here is the link to the excel sheet I mentioned. I don't know enough about the maintenance costs of ca/kalk reactors to finish the sheet as I'd like, but I suspect, as Tom already mentioned, on the cost charts on the excel sheets, with the reactors and the 2 part overlapping, there would come a point when the cost per day crossed and the reactors became cheaper than the 2 part system. And it's based on how much you need per day of cal and alk; but my hunch is that the "cross over" point will be very high. Maybe 500mL/day or more... (IE big tanks or very demanding SPS tanks). My tank for example, is a 135g with a decent amount of SPS, and it demands only 60mL of cal and alk per day. So IMO, a 30g tank, even stuffed with SPS, wouldn't demand much more than 20-40mL/day, and as you can see on the chart, strictly speaking from a cost standpoint, the 2 part is absolutely the cheaper method, in the short term and in the long term. ($0.10-$0.21/day).