I think I need to do more to eliminate phosphates

rhitee93 · Feb 12, 2024

My phosphates keep creeping up even though I have to dose nitrates. This week my phosphates hit 0.43ppm, and I'm thinking about trying lanthanum chloride, or setting up a GFO reactor. Obviously I need to figure out where the phosphates are coming from, but I'm feeling nervous that I need to act to reduce the level in the meantime.

Factual stuff:

120gal display w/sump (108 gal of actual water volume)
I do a 10% water change every week
I use an 8-stage RO/DI system to for my water (sediment, 2 carbon, RO, Cation, Anion, and two mixed bed DI) Water reads 0TDS.
Livestock: Foxface Rabbitfish, Tomini Tang, 2 Clowns, 1 Very small green spotted puffer, 13" snowflake eel
I almost exclusively feed San Francisco Bay brand frozen foods (I have a variety that I pick rom at random)
I feed the fish 2 cubes a day
The eel gets fed 2 ro 3 times a week - scallops, squid, shrimp, salmon that I get from the fish counter
The only coral is a GSP colony that is growing like crazy (I just added a Duncan and Frogspawn, but they've only been in the tank a few days)
The tank is about 6 months old
roller mat, Reef Octo Regal 150-int skimmer, small chaeto ball in fuge, but the photoperiod is very short because of the nitrate issue

Stuff I think is true, but I don't know for sure:

I am thinking that lack of filtration isn't the issue since I am having to dose nitrates to maintain 10.0ppm. I have to add about 3ppm worth of sodium nitrate each week.
I haven't been rinsing my frozen food and I'm wondering if that is the phosphate source. (How do you rinse what is effectively mush?)

Am I panicking for no reason? My phosphates hung out at 0.15ppm for 3 or 4 months. They took a big jump a few weeks ago, and then have gone up by about 0.050 a week for the last few weeks. I don't really know what has changed, but I feel like I need act to reduce the levels while I figure out the cause.

rennjidk · Feb 12, 2024

Either option will be effective in reducing and maintaining phosphates. Just pick whichever option seems easier for you. I don't believe rinsing your food is adding any detectable amount of Po4.

Koty · Feb 12, 2024

Did I miss somthing? You do not dose carbon?

rennjidk · Feb 12, 2024

rhitee93 said:
Am I panicking for no reason? My phosphates hung out at 0.15ppm for 3 or 4 months. They took a big jump a few weeks ago, and then have gone up by about 0.050 a week for the last few weeks. I don't really know what has changed, but I feel like I need act to reduce the levels while I figure out the cause.

If I had to take an educated guess, since you're at the 1 year mark in such a large system and haven't made any changes to nutrient import, it's possible that you're finally hitting the crest of the phosphate binding ability of the rocks and substrate. I have absolutely no idea if that's true or not. One of the chemistry folks would need to chime in for an actual answer.

rennjidk · Feb 12, 2024

Koty said:
Did I miss somthing? You do not dose carbon?

He's already dosing nitrate. There wouldn't be a reason to, unless he's trying to cultivate bacterial populations for filter feeders. Po4 is better controlled through other means.

stevemillersreef · Feb 12, 2024

rhitee93 said:
My phosphates keep creeping up even though I have to dose nitrates. This week my phosphates hit 0.43ppm, and I'm thinking about trying lanthanum chloride, or setting up a GFO reactor. Obviously I need to figure out where the phosphates are coming from, but I'm feeling nervous that I need to act to reduce the level in the meantime.

Factual stuff:

120gal display w/sump (108 gal of actual water volume)

I do a 10% water change every week

I use an 8-stage RO/DI system to for my water (sediment, 2 carbon, RO, Cation, Anion, and two mixed bed DI) Water reads 0TDS.

Livestock: Foxface Rabbitfish, Tomini Tang, 2 Clowns, 1 Very small green spotted puffer, 13" snowflake eel

I almost exclusively feed San Francisco Bay brand frozen foods (I have a variety that I pick rom at random)

I feed the fish 2 cubes a day

The eel gets fed 2 ro 3 times a week - scallops, squid, shrimp, salmon that I get from the fish counter

The only coral is a GSP colony that is growing like crazy (I just added a Duncan and Frogspawn, but they've only been in the tank a few days)

The tank is about 6 months old

roller mat, Reef Octo Regal 150-int skimmer, small chaeto ball in fuge, but the photoperiod is very short because of the nitrate issue

Stuff I think is true, but I don't know for sure:

I am thinking that lack of filtration isn't the issue since I am having to dose nitrates to maintain 10.0ppm. I have to add about 3ppm worth of sodium nitrate each week.

I haven't been rinsing my frozen food and I'm wondering if that is the phosphate source. (How do you rinse what is effectively mush?)

Am I panicking for no reason? My phosphates hung out at 0.15ppm for 3 or 4 months. They took a big jump a few weeks ago, and then have gone up by about 0.050 a week for the last few weeks. I don't really know what has changed, but I feel like I need act to reduce the levels while I figure out the cause.

I started using the little discs that you put between the black blocks from maxspect. It was usually high at 40, now it’s at .02

rhitee93 · Feb 12, 2024

No, I'm not dosing carbon. I don't even know how or why to do that yet. So much to learn in this first year...

rennjidk said:
If I had to take an educated guess, since you're at the 1 year mark in such a large system and haven't made any changes to nutrient import, it's possible that you're finally hitting the crest of the phosphate binding ability of the rocks and substrate. I have absolutely no idea if that's true or not. One of the chemistry folks would need to chime in for an actual answer.

I understand what you are saying, but I don't understand why the nitrates and phosphates are so disconnected. Both are generated from something I'm putting into the tank, so i would think they would both rise proportionally.

Maybe something is using up nitrates but not phosphates? Not sure what it would be. I don't have much algae growing, and not much in the way of coral yet.

rennjidk · Feb 12, 2024

rhitee93 said:
No, I'm not dosing carbon. I don't even know how or why to do that yet. So much to learn in this first year...

I understand what you are saying, but I don't understand why the nitrates and phosphates are so disconnected. Both are generated from something I'm putting into the tank, so i would think they would both rise proportionally.

Maybe something is using up nitrates but not phosphates? Not sure what it would be. I don't have much algae growing, and not much in the way of coral yet.

Nitrates are more quickly consumed in most systems. You'll see a lot of tanks dosing nitrate, but few dosing phosphate once the system becomes saturated. The focus then shifts to phosphate removal.

I think you're searching for a flaw in your method that doesn't exist. So far, everything has been right on track as expected IMO.

rhitee93 · Feb 12, 2024

Thanks for the insight. I've got some lanthanum chloride on the way. Based on what I've read, I'll start out slow to see how the system reacts.

Randy Holmes-Farley · Feb 13, 2024

rhitee93 said:
Obviously I need to figure out where the phosphates are coming from, but I'm feeling nervous that I need to act to reduce the level in the meantime.

Answer: foods.

There's no need to panic, but lowering it is a fine plan. I choose GFO in my system.

rhitee93 · Feb 13, 2024

I experimented with GFO some in the last week, but I just put a few spoonfuls (maybe 1/4 of a cup) in a mesh bag and placed in a high flow part of the sump. I took a very timid approach because I have read so many stories about GFO crashing phosphates to zero quickly. However, the bag of GFO has done nothing to my levels.

It sounds like this is a pretty common experience, and that most feel GFO needs to go in a reactor to be effective. If that is the case, I think I'll try the lanthanum chloride first.

Koty · Feb 13, 2024

I would strongly recomend carbon dosing just to feed the bacterial population. There are some that claim that carbon dosing help corals uptake phosphate. My nitrate is around 0 so I dose both amino acids and carbon as my phosphate is relatively high (0.2-0.1). Bottom line corals are very happy.

rhitee93 · Feb 13, 2024

Koty said:
I would strongly recomend carbon dosing just to feed the bacterial population. There are some that claim that carbon dosing help corals uptake phosphate. My nitrate is around 0 so I dose both amino acids and carbon as my phosphate is relatively high (0.2-0.1). Bottom line corals are very happy.

Thanks! This is something I want to learn about. When I first got back into reefing I saw a post somewhere that talked about carbon dosing being dangerous if done wrong, and not for beginners, so I sort of filed that way for another day, and simply haven't explored it yet.

I'm just starting to add corals now, and will have to up my aquarium chemistry knowledge. I haven't worried about the reef chemistry much up to this point as I was focused on just keeping fish happy.

Koty · Feb 13, 2024

I use carbon dosing reagents from Tropic Marine. They do a great job IME. I have a lot of fish so I use Elimi NP dosed 4 x 1.5 ml /day in 110g and Reef actif once a week. Once nitrates hit 0 I started dosing amino acids. I do not see the point of dosing nitrates in a high bioload tanks as it is probably low but not real 0.