Nice display. Sorry for your loss. What done is done but I would strongly recommend that you properly dispose of the product you used or donate it to someone who has a pool / spa to make better use of it. Lanthanum Chloride is a bit of a mix bag as you can see by the replies here and what you may have read elsewhere.
I think the priority now is to do some water changes as you are doing matching parameters to remove residual. I don't know the shelf life is in the water but maybe Randy here has insight. But continue that course and then recheck your phosphate level and assess.
I don't know what the phosphate number was or what you wanted to reach or if it was even necessary but as already noted a safe product to use would be Blue Life's Phosphate Rx. Similar concept of calculating water volume, math to get number of drops, add slowly to filter sock before skimmer, or drip directly into the skimmer, preferably just before lights out for sleeping / calmer tank, and let it run for a couple days. Then water change. More or less it.
Lastly, because I don't want to kick a dead horse, double check sources that recommend a over the counter product you may add to do something. There are a lot of older articles, and current ones, from chemist such as Randy here that list names of safe products to use. And why that is important is that there is a 99% or higher chance they used the product be it baking soda, pickling lime, or lanthanum chloride. Just something to remember because life is a bit crazy but that extra minute of checking could help down the road.
Again that is a rocking tank you have based on that photo you shared. Keep that skimmer running, do some water changes, easy to get it cleared. Be safe.
Edit: side effects when I used Phsphate Rx:
1. Bubble tips receded a bit for a couple days
2. Leathers, mostly my green long tentacle, closed up a for a few days
I think the priority now is to do some water changes as you are doing matching parameters to remove residual. I don't know the shelf life is in the water but maybe Randy here has insight. But continue that course and then recheck your phosphate level and assess.
I don't know what the phosphate number was or what you wanted to reach or if it was even necessary but as already noted a safe product to use would be Blue Life's Phosphate Rx. Similar concept of calculating water volume, math to get number of drops, add slowly to filter sock before skimmer, or drip directly into the skimmer, preferably just before lights out for sleeping / calmer tank, and let it run for a couple days. Then water change. More or less it.
Lastly, because I don't want to kick a dead horse, double check sources that recommend a over the counter product you may add to do something. There are a lot of older articles, and current ones, from chemist such as Randy here that list names of safe products to use. And why that is important is that there is a 99% or higher chance they used the product be it baking soda, pickling lime, or lanthanum chloride. Just something to remember because life is a bit crazy but that extra minute of checking could help down the road.
Again that is a rocking tank you have based on that photo you shared. Keep that skimmer running, do some water changes, easy to get it cleared. Be safe.
Edit: side effects when I used Phsphate Rx:
1. Bubble tips receded a bit for a couple days
2. Leathers, mostly my green long tentacle, closed up a for a few days