Aquarium Chemistry Question? Ask the Doctor!

[Randy Holmes-Farley]

A bit of chemistry, a bit of reefkeeper knowledge needed Randy.

With the cooling fan off for the season and evap down, I've hit the limit of kalk dosing sooner than I expected @1.1dkh daily. I dose from a still reservoir of saturated kalk via dosing pump.

In threads I've researched, I see you've credited Craig Bingman for the 45ml/gallon vinegar to RODI for roughly 2.72 tspn saturation of limewater. You also caution about the potential for excessive carbon dosing.

So, the reefkeeping part - My system is already attuned to about 60% that vinegar dose and has been doing well. I run no socks or skimmer, only macroalgae-fuge. Since I have no skim, do I run the same risk of overdoing the carbon dose, or is it a non-issue bc the bac aren't being skimmed out?

Anything else I should be concerned about?

ty

My biggest concern is not the lack of skimming but in driving nutrients (e.g., nitrate) too low. People have always worried about what happens to the bacteria, but I expect they will just be eaten by other organisms.

 

[BeejReef]

My biggest concern is not the lack of skimming but in driving nutrients (e.g., nitrate) too low. People have always worried about what happens to the bacteria, but I expect they will just be eaten by other organisms.

ty, I'll keep an eye on N. It is a touch lower than I'd like, but is pretty stable at 3-5ppm. P is my struggle. I have to dose it and don't really understand why. I feed two cubes a day, 1-2 times a week w reef chili... as I said, no mechanical filtration at all. It just disappears. Maybe twice, I've overdone it up to .35, and it's 0.0 within two days.

Been walking the fuge back from 14 hours reverse, down to 7 hours now over the course of a few months. It's a good problem to have I guess. I just wish I understood it. Also, I've had the issue with undetectable P for a good 4 months, well before I began any sort of carbon dosing.

 

[BGrand]

Good Morning

I have had my tank setup and running for over a year now (54 corner with sump for total of 58 gal. after rock and sand) and really want to start dialing some numbers in. Currently my testing shows the following:

• NO3 = 4.0 ppm
• pH = 8.27
• PO43 = 0.64 ppm
• Alk = 7.4 dKH
• Cal. = 394 ppm
• Salinity = 1.024

These numbers are pretty consistent without dosing anything but Red Sea NOPOX at 5 ml/day. I will eventually stop dosing that as I dial my feeding in a little better. My coral are starting to consume quite a bit of calcium so I started dosing a little calcium once a week and just purchased two dosing pumps. One I am using for NOPOX the other I plan on starting to dose calcium and when I stop the NOPOX switching it to Alk.

I religiously perform a 10% - 20% water change weekly. I change my sock out and scrape my algae scrubber weekly as well.

I created a spreadsheet that I track all my testing on in January of last year. My question is I have conditional formatting set up on my spreadsheet with ranges but I'm not really sure what those ranges should be. Could you help by giving me some ranges for the chemistry in my tank? Currently my ranges are set as follows with the goal being somewhere in the middle:

• NO3 = 0 - 25 ppm
• pH = 7.6 - 8.7
• PO43 = 0 - 0.5 ppm
• Alk = 8.0 - 9.0 dKH
• Cal. = 390 - 470 ppm
• Salinity = 1.023 - 1.027

 

[Michael Frank]

I was going to use this food-grade calcium chloride for dosing. Do you see any issue with the composition?


The attached image is the Composition I received from the Manufacture

 

[Dkeller_nc]

Good Morning

I have had my tank setup and running for over a year now (54 corner with sump for total of 58 gal. after rock and sand) and really want to start dialing some numbers in. Currently my testing shows the following:

• NO3 = 4.0 ppm
• pH = 8.27
• PO43 = 0.64 ppm
• Alk = 7.4 dKH
• Cal. = 394 ppm
• Salinity = 1.024

These numbers are pretty consistent without dosing anything but Red Sea NOPOX at 5 ml/day. I will eventually stop dosing that as I dial my feeding in a little better. My coral are starting to consume quite a bit of calcium so I started dosing a little calcium once a week and just purchased two dosing pumps. One I am using for NOPOX the other I plan on starting to dose calcium and when I stop the NOPOX switching it to Alk.

I religiously perform a 10% - 20% water change weekly. I change my sock out and scrape my algae scrubber weekly as well.

I created a spreadsheet that I track all my testing on in January of last year. My question is I have conditional formatting set up on my spreadsheet with ranges but I'm not really sure what those ranges should be. Could you help by giving me some ranges for the chemistry in my tank? Currently my ranges are set as follows with the goal being somewhere in the middle:

• NO3 = 0 - 25 ppm
• pH = 7.6 - 8.7
• PO43 = 0 - 0.5 ppm
• Alk = 8.0 - 9.0 dKH
• Cal. = 390 - 470 ppm
• Salinity = 1.023 - 1.027

Those parameter ranges look fine, although if you intend to keep SPS you'd like your specific gravity to be a little more stable. Fortunately, that's fairly easy with an auto top-off unit; you should be able to keep the specific gravity 1.026 +/- 0.001 with virtually no effort on your part except for occasionally filling the reservoir.

pH generally isn't worth measuring, with the only exception being tanks kept in tightly sealed homes where CO2 builds up and causes really low pH; typically, you'd like the pH to remain above 7.8 throughout the day/night cycle (pH will naturally drop overnight, with the lowest reading typically being in the morning right before the lights come on).

Finally, the important point about alkalinity is that it remain stable, at least for SPS corals. Generally, people find that alkalinity additions must be done once per day if dosed manually, or they use a dosing pump to add small amounts throughout the day.

 

[Dkeller_nc]

I was going to use this food-grade calcium chloride for dosing. Do you see any issue with the composition?


The attached image is the Composition I received from the Manufacture

Since this is food-grade calcium chloride, it should be fine for use in a reef tank.

 

[BGrand]

Those parameter ranges look fine, although if you intend to keep SPS you'd like your specific gravity to be a little more stable. Fortunately, that's fairly easy with an auto top-off unit; you should be able to keep the specific gravity 1.026 +/- 0.001 with virtually no effort on your part except for occasionally filling the reservoir.

pH generally isn't worth measuring, with the only exception being tanks kept in tightly sealed homes where CO2 builds up and causes really low pH; typically, you'd like the pH to remain above 7.8 throughout the day/night cycle (pH will naturally drop overnight, with the lowest reading typically being in the morning right before the lights come on).

Finally, the important point about alkalinity is that it remain stable, at least for SPS corals. Generally, people find that alkalinity additions must be done once per day if dosed manually, or they use a dosing pump to add small amounts throughout the day.

Thank you very much for your help!

 

[bam123]

I have a 60 cube mixed reef, barebottom. I am currently using GFO but am considering using a macroalgae reactor or brightwell phosphate E. Thoughts on which way you would go would be appreciated. Thx

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Thanks!

 

[Dkeller_nc]

I have a 60 cube mixed reef, barebottom. I am currently using GFO but am considering using a macroalgae reactor or brightwell phosphate E. Thoughts on which way you would go would be appreciated. Thx

This is probably better answered in the main Reef Chemistry forum, since the "Ask the Doctor" is generally aimed at beginning reefer questions with definitive answers like "how do I calculate how much calcium solution to add to go from Xppm to Yppm".

As far as your particular question, you'll get a lot of opinions, since the reef hobby is a crowd-sourced knowledge base generated through lots of trial and error. The three methods you mention all have their adherents, but here's a few comments that may help you make your decision.

Macro algae reactors/refugiums can be quite effective at reducing both phosphate and nitrate in established tanks with a relatively high bioload. The do, of course, require more equipment and add plumbing complexity over using lanthanum chloride or GFO as chemical means to reduce phosphate, and macro algae reactors/refugiums tend not to perform very well in newly established tanks or tanks without a heavy bioload since it can be difficult to get the macro algae to grow in tank water that's already low in nutrients.

The lanthanum chloride method is usually chosen when the phosphate concentration is quite high, and it'd be expensive to absorb so much phosphate with GFO. One caution about LaCl2 phosphate reduction - it's critically important that it be dosed in a carefully calculated manner so that all of the LaCl2 is converted to lanthanum phosphate, and it's also very important that the aquarist dose it into a reef sock or other filtration apparatus that will effectively remove the precipitated LaPO4. LaPO4 solids are strongly suspected to be toxic to certain fish species, such as tangs.

GFO is probably the easiest approach, though definitely not the least expensive. The only real thing that can go wrong with GFO is that the aquarist uses too much of it and sharply drops the PO4 concentration of the water to nearly zero. That can have a very bad effect on SPS in general and acropora in particular. So one will want to start with small amounts of GFO, and gradually lower the phosphate concentration in the water over a 6 week period to your target level.

 

[GeoSquid]

Question: I've had a situation where my Alk was running at 11 dkh and my CA was 380. Some time ago, I wanted to up my ALK from 8 dkh and started adding extra baking soda and slowed my Kalk addition. I think this is how it got out of whack. In reading one of Randy's chemistry articles it stated to start adding Ca Chloride. So, over the last week and a half I've added 30 tsp of dry Ca Chloride to my 180 gal tank. I am now testing 9 dkh Alk and 340 Ca. Why is my Ca dropping?

 

[Dkeller_nc]

Presuming you're using calcium chloride dihydrate, 30 teaspoons is approximately 165 grams, of which 27% is actually calcium (the rest is chloride and water). That means that you've added 165*0.27 = 45 grams. If your tank volume is actually 180 gallons (could be less, could be more depending on the presence of a sump and how much "reef" you have in it), that amount of calcium equates to 66 ppm. That's not a lot of calcium, and presuming that you have a fair amount of coral or coralline algae, that amount and more could easily be consumed in a week.

 

[GeoSquid]

Presuming you're using calcium chloride dihydrate, 30 teaspoons is approximately 165 grams, of which 27% is actually calcium (the rest is chloride and water). That means that you've added 165*0.27 = 45 grams. If your tank volume is actually 180 gallons (could be less, could be more depending on the presence of a sump and how much "reef" you have in it), that amount of calcium equates to 66 ppm. That's not a lot of calcium, and presuming that you have a fair amount of coral or coralline algae, that amount and more could easily be consumed in a week.

It's probably pretty close to 180 gal, pretty minimal aquascaping. Mostly soft coral and not a lot of coralline algae. I started with all dead base rock about a year and a half ago. Thank you for the response , that is good to know. I was going by the BRS calculator for their Calcium Chloride.

 

[Dkeller_nc]

There are two other aspects to this. One is simply abiotic precipitation of calcium carbonate. In tanks without a lot of organics in the water, and especially if the tank water is low in magnesium (or you're using a salt mix that is fairly low in magnesium), you can get a fair amount of abiotic precipitation of calcium carbonate when calcium chloride is added to water with a fairly high alkalinity (i.e., alk >10 dKH). One way to check for this is to look at the outside of a heater and/or the interior impeller of a circulation or return pump. If the tank's predisposed to abiotic precipitation of calcium carbonate, these surfaces will accumulate it first. Abiotic precipitation of calcium carbonate isn't a big deal unless it's sufficiently bad to be trashing your pumps, so it's probably not worth buying a magnesium test if your corals don't need that element (and within reason, soft corals don't).

Another aspect is that hobbyist calcium tests aren't terribly accurate - generally any reading that's +/- 20 ppm should be considered "no change".

 

[BurgerFish]

I have a 100g total water volume with 6 small fishes, crabs and snails.

Hanna ULR Phosphorus shows 0 ppb. I run skimmer, refugium and dose bio mate twice weekly.

0 ppb is good or lack of phosphates?

 

[Dr. Reef]

Ideally you would want some phosphates. Normally between 0.03 to 0.05

 

[BurgerFish]

Ideally you would want some phosphates. Normally between 0.03 to 0.05

Nitrates also zero.

What to do? Add more fishes, reduce fuge light? Add more food?

 

[Dr. Reef]

0 nitrates is also not ideal. Normally would like to have 5 to 10 ppm.
Feed a little more if fish can consume it. Shorten refuge lighting schedule, reduce the algae a little.

 

[BurgerFish]

8h for fuge is ok? Now it's 12h.

4h without fuge light won't cause pH drop from CO2?

 

[Dr. Reef]

Spread it out. Do 2 hours less in the beginning and 2 hours less at the end.

 

[Haim]

How often do you change water? Maybe replace 10% a week?