High Po4 In RODI - Salt Mix Really Reason?

[RMS18]

Hey everyone,

So i have always faced a po4 issue in my system, hard to ever keep it consistent around the .05-.08 without phosphate rx daily. This issue had lead me to carbon dosing which brought me into the Dino world. I have gotten past the dinos now and stopped the carbon but cyano is a big issue and will not ease up. My tank will rise to .25 without phosphate rx, my feeding is fine 120g 3 cubes a day with 8 fish. I have a cheato fuge, and 20lb of LR in the sump and 75lb in my display.

So i decided to test my freshly made s/w, Hanna ULR. I was getting readings of .08 and .1ppm when converted. I have a 7 stage BRS rodi system, i run the 3 stage DI resin, and the resin is new and not color changing yet. Carbon blocks and sediment is new and membranes (qty 2) are 8 months old. I then pulled fresh RODI on the exit lines before going into the brute can, mixed it and it tested po4 at the similar numbers, .06-.1.

I called BRS, they had me test the TDS in my tap water, reading 200ppm. They see no issues with my resin or membranes. So they asked what salt i used, HW Marinemix. They then stated that it's possible HW and Tropic Marine elevate their PO4 to mirror NSW.... isn't .08-.1 is a bit high for NSW? I tried 2 different batch # of my Hanna reagent, along with 2 different batches of HW marinemix salt.

I hooked up a small reactor with GFO for now to strip the new SW, and if i find it is the salt then i may have to do something more permanent with the reactor, as i like the alk level on this salt.

Thoughts on this issue being the salt?

 

[RMS18]

Don't all jump in at once!

My cousin uses the same salt as I do. He also has IO he is using for qt right now. His Hanna checker is not the UL version so it can read po4 in fresh water. I had him measure his rodi water which came out to .02 of po4. Then he mixed some HW Marinemix salt to 1.026 and po4 read .1ppm! I had him test IO salt and that read .02. I think it's fair to say HW does add po4, a bit more than I'd like. Time to look for a new salt.

 

[chipmunkofdoom2]

Hobbyists historically have decided that there's a link between cyano and high phosphate, but I don't know if the solution is reduce phosphate to only a couple parts per billion. As you noticed, driving nutrients down caused other issues.

Why do you think 0.25 ppm phosphate is too high? Is cyano the only reason? Many SPS tanks have phosphates of 0.5 ppm or higher and are very healthy.

 

[Randy Holmes-Farley]

I then pulled fresh RODI on the exit lines before going into the brute can, mixed it and it tested po4 at the similar numbers, .06-.1.

That phosphate level (0.05 to 0.1 ppm) is totally insignificant when used for normal water changes or for top off, relative to the 10-100 times as much that you add each date in foods. It may not seem low, but you have to consider the big dilution effect when used, and on the much larger sources.

Focus on foods and export, not on that " small" level in RO/DI or new salt water.

I show that here:

Aquarium Chemistry: Phosphate And Math: Yes You Need To Understand Both

Foods are by far the most important source of phosphate in most aquariums. In considering whether sources of phosphate other than foods are important, one must carefully look to the actual amounts involved to determine whether other sources are even worth trying to minimize.

reefs.com

from it:


Comparison of Food Sources of Phosphate to Other Sources
What about other sources of phosphate, like the “crappy” RO/DI water containing 0.05 ppm phosphate? A similar analysis will show it equally unimportant relative to foods.

Let’s assume that the aquarist in question adds 1% of the total tank volume each day with RO/DI to replace evaporation. Simple math shows that the 0.05 ppm in the RO/DI becomes 0.0005 ppm added each day to the phosphate concentration in the aquarium. That dilution step is critical, taking a scary number like 0.05 ppm down to an almost meaningless 0.0005 ppm daily addition. Since that 0.0005 ppm is 40-600 times lower than the amount added each day in foods (Table 4), it does not seem worthy of the angst many aquarists put on such measurements. That said, tap water could have as much as 5 ppm phosphate, and that value could then become a dominating source of phosphate and would be quite problematic. Purifying tap water is important for this and many other reasons.

 

[RMS18]

Hobbyists historically have decided that there's a link between cyano and high phosphate, but I don't know if the solution is reduce phosphate to only a couple parts per billion. As you noticed, driving nutrients down caused other issues.

Why do you think 0.25 ppm phosphate is too high? Is cyano the only reason? Many SPS tanks have phosphates of 0.5 ppm or higher and are very healthy.

Well I brought po4 up to .2-.25 to help combat dinos, along with a million other things I tried for almost a year. Turns out by stopping all the changes and additives, and just keeping the big 3 stable and po4 and no3 back into a normal range with regular maintenance again the dinos went away.

Once they went away, cyano came in. Don't misunderstand I'm not shooting for uln, my goal is .05-.08ish. However I have very slow growth, and when a new sps frag is added, let takes a strawberry shortcake for example. The coral will darken, the bright red darkens to a brownish red.

High po4 may work in a mature sps tank, but not in a 1.5 year old tank with 10 one inch frags. Lastly the abundance of green algae growth was also a indicator nutrients were to high.

The salt now will start me off at .1, by the time I'm ready for a w/c po4 is at .2+. So if start with a salt that doesn't add po4 by the time I do a w/c levels should be within the goal range.

 

[Dkeller_nc]

As Randy notes, the 100 ppb or so in your finished ASW for water changes just isn't a contributing factor unless you're really doing huge water changes in the 50% or greater range. To put a few more details on his answer about the amount of phosphate in the fish food you're adding:

A "cube" of fish food weighs about one tenth of an ounce, or 2.83g. Of that weight, the phosphate content will be about 2 mg/g, so each cube of fish food will add about 6 mg of phosphate. I'm interpreting from your signature line that you've a 120 gallon tank, so that means that you're adding 18 mg/120 gallons or around 40 ppb per day. Without active removal, I think you can see that the phosphate concentration in your tank will continue to rise significantly week to week.

One note about this - do NOT attempt to control nutrients in your tank by restricting your fishes' nutrition. There are many other ways to accomplish nutrient export and control that don't impact your fishes' health.

 

[RMS18]

That phosphate level (0.05 to 0.1 ppm) is totally insignificant when used for normal water changes or for top off, relative to the 10-100 times as much that you add each date in foods. It may not seem low, but you have to consider the big dilution effect when used, and on the much larger sources.

Focus on foods and export, not on that " small" level in RO/DI or new salt water.

I show that here:

Aquarium Chemistry: Phosphate And Math: Yes You Need To Understand Both

Foods are by far the most important source of phosphate in most aquariums. In considering whether sources of phosphate other than foods are important, one must carefully look to the actual amounts involved to determine whether other sources are even worth trying to minimize.

reefs.com

from it:


Comparison of Food Sources of Phosphate to Other Sources
What about other sources of phosphate, like the “crappy” RO/DI water containing 0.05 ppm phosphate? A similar analysis will show it equally unimportant relative to foods.

Let’s assume that the aquarist in question adds 1% of the total tank volume each day with RO/DI to replace evaporation. Simple math shows that the 0.05 ppm in the RO/DI becomes 0.0005 ppm added each day to the phosphate concentration in the aquarium. That dilution step is critical, taking a scary number like 0.05 ppm down to an almost meaningless 0.0005 ppm daily addition. Since that 0.0005 ppm is 40-600 times lower than the amount added each day in foods (Table 4), it does not seem worthy of the angst many aquarists put on such measurements. That said, tap water could have as much as 5 ppm phosphate, and that value could then become a dominating source of phosphate and would be quite problematic. Purifying tap water is important for this and many other reasons.

What has me stuck is if the water column has .2 and i take out 50% of the water and add in new sw that contains .1, then in reality it's like adding back 50% of the water i took out and 50% of truly clean water. So at the end of the day i did a 25% w/c rather than a 50%?

I have 2 boxes of HW Marineminx left, i hooked up a GFO reactor to the sw bin, po4 dropped to .02 overnight. Over the next few weeks i'll monitor po4 levels without the use of any po4 reduces outside my fuge. Curious to see if they stay more stable within the range id like.

 

[chipmunkofdoom2]

Don't misunderstand I'm not shooting for uln, my goal is .05-.08ish. However I have very slow growth, and when a new sps frag is added, let takes a strawberry shortcake for example. The coral will darken, the bright red darkens to a brownish red.

I asked why 0.25 ppm of phosphate was concerning to you because I suspected that you, like most people who ask the question, were having an algae problem and wanted to get rid of it. Starving algae out just really doesn't seem to work that well. If you want to get rid of algae, get rid of the algae: get urchins, more snails/crabs or tangs to consume it. Algae just doesn't seem to be that sensitive to reduced dissolved nitrate and phosphate.

Also, 0.05 - 0.08 ppm is low for phosphate. It may not be the textbook definition of ULNS, but more and more reefers are keeping their phosphate levels much higher than that these days and have great success, even with SPS. There also isn't really any compelling evidence that higher phosphates are okay in old tanks but not in new tanks. Colors darkening usually are due to high nitrates rather than high phosphates.

Like many others who have tried to starve out algae by driving nutrients down close to zero (including myself), you had a dino outbreak the last time you tried that approach. I would be surprised if you got a different result from doing the same thing again, but either way, please let us know your results.

 

[RMS18]

As Randy notes, the 100 ppb or so in your finished ASW for water changes just isn't a contributing factor unless you're really doing huge water changes in the 50% or greater range. To put a few more details on his answer about the amount of phosphate in the fish food you're adding:

A "cube" of fish food weighs about one tenth of an ounce, or 2.83g. Of that weight, the phosphate content will be about 2 mg/g, so each cube of fish food will add about 6 mg of phosphate. I'm interpreting from your signature line that you've a 120 gallon tank, so that means that you're adding 18 mg/120 gallons or around 40 ppb per day. Without active removal, I think you can see that the phosphate concentration in your tank will continue to rise significantly week to week.

One note about this - do NOT attempt to control nutrients in your tank by restricting your fishes' nutrition. There are many other ways to accomplish nutrient export and control that don't impact your fishes' health.

I would never try to reduce po4 by cutting on feedings. My fish are more important to me than corals IMO. Well outside permanently running GFO, not sure what else could be done. Running a NYOS 160 skimmer, fuge has basketball size clump of healthy cheato and the light run 18 hours a day. Filter pads are changed daily. Weekly 20-25% w/c with sand cleaning.

 

[RMS18]

I asked why 0.25 ppm of phosphate was concerning to you because I suspected that you, like most people who ask the question, were having an algae problem and wanted to get rid of it. Starving algae out just really doesn't seem to work that well. If you want to get rid of algae, get rid of the algae: get urchins, more snails/crabs or tangs to consume it. Algae just doesn't seem to be that sensitive to reduced dissolved nitrate and phosphate.

Also, 0.05 - 0.08 ppm is low for phosphate. It may not be the textbook definition of ULNS, but more and more reefers are keeping their phosphate levels much higher than that these days and have great success, even with SPS. There also isn't really any compelling evidence that higher phosphates are okay in old tanks but not in new tanks. Colors darkening usually are due to high nitrates rather than high phosphates.

Like many others who have tried to starve out algae by driving nutrients down close to zero (including myself), you had a dino outbreak the last time you tried that approach. I would be surprised if you got a different result from doing the same thing again, but either way, please let us know your results.

NO3 stays around 8ppm, which i believe shows no problem there. When you have a mature tank "packed" with corals vs a box of water, those corals become a export system in a way, being the dominant consumer of available nutrients. I believe this for not only have i read/watched it, but i have another tank LPS (10gallon, no skimmer, no fuge, no reactor, just a rock, powerhead, light and water), than runs .04 and 1ppm of nitrate and i have a hard time keeping those levels there without dosing after w/c. Corals are thriving and outgrowing the tank. However it was not always like that. Until it became heavy in happy corals, nutrient levels did climbs to the .15-.2 on po4 and 10-15 of no3.

Not saying your wrong in anyway, just trying to figure out what works for this 120 of a nightmare lol.

There was a short 3 month period after the first Dino fight where the tank was amazing, growth was great, colors were awesome. I go back into my logs in apex and read what my parameters were, everything was the same but po4 and no3 (during this time i was not doing w/c).

 

[Dkeller_nc]

By the way - I'm not accusing you of restricting your fishes' diet necessarily; on forums, one doesn't have the whole picture of a particular person's knowledge, and because it's quite common to see that approach (restricting food input to a tank) and lots of folks read through old threads looking for solutions, adding the note about continuing to feed normally was worthwhile.

With respect to running GFO in your ASW container, also realize that depending on how much GFO you're running, it may depress the alkalinity and calcium - GFO provides a surface for abiotic precipitation of calcium carbonate, which is one reason that the procedure for regenerating GFO contains an initial acid-wash step. The effect may not be pronounced enough to matter, but it'd be worth testing the ASW for calcium and alkalinity to make sure.

 

[Randy Holmes-Farley]

What has me stuck is if the water column has .2 and i take out 50% of the water and add in new sw that contains .1, then in reality it's like adding back 50% of the water i took out and 50% of truly clean water. So at the end of the day i did a 25% w/c rather than a 50%?

I have 2 boxes of HW Marineminx left, i hooked up a GFO reactor to the sw bin, po4 dropped to .02 overnight. Over the next few weeks i'll monitor po4 levels without the use of any po4 reduces outside my fuge. Curious to see if they stay more stable within the range id like.

If only it were that simple. lol

If you have 0.3 ppm and do even a 100% water change with 0.000 ppm water, you will only drop phosphate a small amount because by far the majority of the available phosphate is bound to rock and sand and will be released when you try to lower phosphate. For that reason, water changes are never a good way to lower phosphate.

 

[Joedubyk]

I think nutrients aren't the boogey man we've been told all these yars either

I am finding the best growth and color are coming from high(er) nutrients 25ppm nitrate, and .1-ish phosphate

You have a MUCH better chance of killing your corals, killing color, and growth with too low of nutrients.

have HIGH import and HIGH export. Do not chase super low #s. the risk reward is way worse than bein ga little too high. FWIW, ALL the vendors who get excellent growth and colors and do this for a living keep higher nutrients than what gets parroted on the boards.

 

[RMS18]

Thanks for all the input! I definitely don't understand some of the chemistry in this scenario however most haven't steered me wrong before. Going to give the tank some more time and maintain my regular maintenance to see if things improve.