Phosphate rx and water changes

[Redbird5]

The last two months I've been battling GHA and my phosphates are too high. I've been doing weekly water changes the last three weeks and last weekend on Sunday I used Phosphate Rx on the advice of my LFS. They suggested to use Phosphate Rx before water change. Chatgpt says wait a day before doing a water change. I'm not going to trust AI completely, but I'd like a second opinion.

 

[castellanamattia]

The last two months I've been battling GHA and my phosphates are too high. I've been doing weekly water changes the last three weeks and last weekend on Sunday I used Phosphate Rx on the advice of my LFS. They suggested to use Phosphate Rx before water change. Chatgpt says wait a day before doing a water change. I'm not going to trust AI completely, but I'd like a second opinion.

How large is your tank, and how much water do you change during a water change?

 

[Redbird5]

45g and 10g water change.

 

[jmaneyapanda]

This product is lanthanum chloride. The reason the LFS likely told you that is because it rapidly precipitates phosphate into larger particles that need to be mechanically filtered out. Ideally by floss or a sock, but also by skimming, or worst case, water change. Just be sure you are not overdosing. It will QUICKLY reduce phosphate, which can be bad for corals.

 

[Redbird5]

This product is lanthanum chloride. The reason the LFS likely told you that is because it rapidly precipitates phosphate into larger particles that need to be mechanically filtered out. Ideally by floss or a sock, but also by skimming, or worst case, water change. Just be sure you are not overdosing. It will QUICKLY reduce phosphate, which can be bad for corals.

I'm very careful with it. I know it can mess with coral and fish (wrasses).

 

[Fish Fan]

What is your phosphate concentration? Many times it's not as bad as people may think.

Doing water changes alone is not a good strategy for reducing phosphate because phosphate binds to and is released from rock and sand. So if you take out say 50% of the water, it will drop the phosphate by 50% in the very short term, but very quickly the rock will release more phosphate, and the level goes right back up again.

I'm also not sure if a water change is a good way to remove the precipitate from Lanthanum Chloride dosing, as mentioned, it's usually dosed in a sock for example.

Definitely don't bottom out the phosphate with the LC, zero phosphate is a bigger problem than high phosphate

 

[Fish Fan]

I follow the suggestions from Randy Holmes-Farley on where to keep parameters. Here's his post on that:

Randy’s Thoughts on Nutrient Target Ranges

Thoughts on Nutrient Target Ranges by Randy Holmes-Farley Almost nothing in the world of reef aquarium chemistry causes as much discussion as selecting and maintaining ranges for nitrate and phosphate. Some aquarists want low targets, some want...

www.reef2reef.com

From the above post:
4. What targets seem reasonable? Of course, that depends on all the other factors at play, such as types of corals, availability of ammonia, particulate foods, etc. However, for a mature mixed reef, this would be how I personally would run it:

• Let nitrate float between 5 ppm and 50 ppm. I’d use gentle export in this range, such as growing macroalgae.
• Above 50 ppm, I’d begin to focus more on reducing it, by organic carbon dosing, turf or macroalgae, etc.
• Below 5 ppm, I’d begin to dose ammonia or feed more. The target level might drop lower if dosing ammonia, just like the heavy in/heavy out scenario where nitrate may not be as needed.
• Let phosphate float between about 0.06 ppm and 0.3 ppm. This range is higher than I’ve recommended in the past. I’d use gentle export in this range, such as growing macroalgae.
• Above about 0.3 ppm, I’d begin to focus more on reducing it, by turf or macroalgae, or a binder such as GFO or lanthanum (has its own risks to tangs). If a binder: GO SLOW. Turf and macroalgae will typically be slow enough.
• Below 0.06 ppm, I’d begin to dose sodium phosphate or feed more to get the level up.

I hope this helps and good luck!

 

[Redbird5]

What is your phosphate concentration? Many times it's not as bad as people may think.

Doing water changes alone is not a good strategy for reducing phosphate because phosphate binds to and is released from rock and sand. So if you take out say 50% of the water, it will drop the phosphate by 50% in the very short term, but very quickly the rock will release more phosphate, and the level goes right back up again.

I'm also not sure if a water change is a good way to remove the precipitate from Lanthanum Chloride dosing, as mentioned, it's usually dosed in a sock for example.

Definitely don't bottom out the phosphate with the LC, zero phosphate is a bigger problem than high phosphate

My phosphate level yesterday was 2.7. I have a fair amount of GHA that I've been removing, but of course it's on the rock and I swear it ducks the hose when I try to suck it out. The box says add it to a fast current in the display, both you and my LFS said to dose it in the sock, what's the best method?

 

[Fish Fan]

I haven't used LC in years, but when I did it was in the sock. I think the sock is ideal because then you're catching all the precipitate. The directions on the box may assume that the tank's filtration or water changes will remove the precipitate, that may be a fine way to do it too, I'm not sure.

Phosphate at 2.7 if accurate is high, it's almost certainly coming off the rocks. I think what you may see is high phosphate for some time, and then it will suddenly drop off as what's bound up in the rocks finally gets depleted. I'd watch for that time, that's when you'd be in danger of dropping the phosphate to zero.

You may also want to post this over in the Chemistry subform, and let @Randy Holmes-Farley take a look, I'm sure he would have some suggestions for you.

 

[Randy Holmes-Farley Verified Community Expert]

I’ve never used lanthanum and probably would not unless the levels did get very high like they are here, but I can see various pros and cons of when to use it with respect to water changes.

Overall, I don’t think there’s any clear winner for any particular timing. I’d just do it when it is convenient.

 

[Redbird5]

I haven't used LC in years, but when I did it was in the sock. I think the sock is ideal because then you're catching all the precipitate. The directions on the box may assume that the tank's filtration or water changes will remove the precipitate, that may be a fine way to do it too, I'm not sure.

Phosphate at 2.7 if accurate is high, it's almost certainly coming off the rocks. I think what you may see is high phosphate for some time, and then it will suddenly drop off as what's bound up in the rocks finally gets depleted. I'd watch for that time, that's when you'd be in danger of dropping the phosphate to zero.

You may also want to post this over in the Chemistry subform, and let @Randy Holmes-Farley take a look, I'm sure he would have some suggestions for you.

I'm mixing water now.