Phosphates

[Donya]

Sorry if this is the attack of the dumbo questions but I can't find the answers anywhere. All over the place it says basically "phosphates are bad!" but I have yet to see a chemical reason for why this is the case. The only explaination I've read is that "it can cause algal blooms" (as it does in freshwater as well), but that's not satisfactory for me since all algal blooms are not equal in their effects, positive or negative. So, I am wondering...other than the algae reason:

- Is there any reason that it could have a negative impact on inverts, assuming all other water params are in fine? Supposing just pure phosphate ions floating around in saltwater and no algae problems.

- Is there anything in interacts with or binds with in marine conditions that causes it to be "bad"?

- Is an effect on Ph a consideration for why it is bad?

- When speaking of "phosphates" in the marine aquarium, is this strictly the phosphate ion PO4(-3) or does it include things like phosphoric acid H3PO4, dihydrogen phosphate H2PO4(-1), and monohydrogen phosphate HPO4(-2)?


That last one is a bit obscure and nitpicky, but it makes a difference for some things I'm investigating for aquarium ussage in specific circumstances (CaHPO4 to be precise, which has bizzarely shown no evidence of being able to cause algal blooms in freshwater so far).

 

[RoyalGrammaPrincessHannah]

Ive been wondering the same thing. But I can tell you that the different types of phosphate all matter because I heard [from superman] that you need to make sure the test kit tests for all phosphate.

 

[Fish Fingers]

I beleive they are bad for corals. I know you can't have any when you keep SPS.

 

[Ed4567]

The behaviour of phosphate in saltwater is quite complicated.

Inorganic phosphate takes a number of forms, under normal conditions mostly consisting of PO4(3-) and HPO4(2-), though this is dependant on pH. There is a large amount of ion pairing particularly by PO4(3-) with magnesium and calcium (this is why a large amount of phosphate exists as PO4(3-) by LeChateliers principle), and complexes may be formed. At a higher pH the concentration of H+ decreases so less phosphate will exist as HPO4(2-) and more as PO4(3-).

The ion pairing inhibits calcification causing problems with hard corals, and I'm guessing might be a problem for invertebrates when they molt though I'm not sure.