Chemistry help needed

[seabass]

My seagrass lagoon is in need of phosphates and nitrates and I found a source for KNO3 (potassium nitrate) and KH2PO4 (monopotassium phosphate). Here’s my question: is there a difference between KH2PO4 and KPO4; if so, is one more suitable for a marine application (like pH differences)? I have ordered some KH2PO4, but want to make sure that this is what I should be using.

[Reef Gator]

There is no such thing as crystalized KPO4. You meant K3PO4 maybe? And yes, KH2PO4 will create a more acidic solution than K3PO4. You could make a solution from a mixture of the two to get an intermediate pH.

 

Wouldn't it be easier to throw in a few cubes of frozen brine shrimp?

[seabass]

Thanks Reef Gator! That gets me heading in the right direction. It looks like there are three forms: K2HPO4, KH2PO4, and K3PO4. I’m not sure that I’ll be adding enough to affect pH, but I’ll continue monitor it to be sure. This tank has a light bio-load and I already feel that I’m overfeeding. Therefore, I’m thinking that dosing nitrate and phosphate might be advantageous.

[seabass]

Today I picked up some Seachem Flourish Phosphorus (P2O5). It is marketed as a freshwater planted aquarium fertilizer, but I don’t know why it couldn’t be use in a saltwater application. Any idea if P2O5 is alright for marine aquaria?

[Chupacabras]

It should be fine but the cost will become prohibitive quite quickly. Try going the dry fert route to avoid introducing all the garbage that's in the Seachem products.

 

I've done business with Greg Watson before and his service is top notch for ferts.

 

Just a warning, when dosing ferts you should do substantial weekly water changes (50%ish) to "reset" your levels since you should probably be dosing potassium, phosphate and nitrate and a wierd imbalance of the three can cause some nasty issues.

 

Good luck.

[seabass]

Thanks Chupacabras! I got my order from Greg Watson today.

 

I was surprised how fast the order came; I thought that I’d have to dose the Flourish Phosphorus for a while longer. I’m experimenting with CO2 as well; today I witnessed its affect on pH.

[Reef Gator]

Careful with that KH2PO4 as well. By itself it will have a pH of about 4.8.

[Chupacabras]

Are you going with a CO2 reactor or direct injecting with a bottle?

[MJD]

I have no idea but I just aced my chem midterm!

 

MJD

[seabass]

Careful with that KH2PO4 as well. By itself it will have a pH of about 4.8.

That’s great information, thanks. I’m not sure how much I’ll be dosing yet, so I’ll probably just watch the pH for awhile. I’m kind of thinking that I should just dose KH2PO4 and deal with the pH separately. I’m dosing ESV B-Ionic Calcium Buffer and ESV B-Ionic Magnesium to help. However, it would be nice to have a plan if pH remains too low; any other ideas?

 

I don’t know where to get K3PO4? What about using Trisodium phosphate (TSP) Na3PO4? I read that it is also very alkaline. However, since it’s high in sodium, would I have to worry about salinity (and if I dilute it down, would all the other elements become deficient)? I’m thinking that this would make managing salinity a nightmare.

 

 

Are you going with a CO2 reactor or direct injecting with a bottle?

I’m using a CO2 reactor with a solenoid on a timer:

 

The HOB’s filter intake tube is setup as the diffuser:

 

 

I have no idea but I just aced my chem midterm!

Sweet! I kind of wish that I had taken chemistry at some point.

[Reef Gator]

The best way to deal with the pH of your phosphate solution would be to raise the pH with potassium hydroxide (KOH). Here's one site that carries it.

 

http://chemistrystore.com/potassium_hydroxide.htm

 

They also carry dibasic potassium phosphate btw.

 

This would obviously be easier if you had a pH probe, but you should be able to develop a recipe through a few calculatoins (or alittle trial and error).

 

Do be careful with the KOH if you go that route...nasty caustic stuff. Wear gloves!

[seabass]

Do be careful with the KOH if you go that route...nasty caustic stuff. Wear gloves!

Wow, a hazmat waiver form! I really appreciate all the help. At 90% purity, is the other 10% fillers and/or stabilizers (anything that I should be concerned about for a marine tank)? Thanks again.

[Reef Gator]

At 90% purity, is the other 10% fillers and/or stabilizers

 

Good eyes Seabass. I checked the stuff we have in the lab and it is >85% pure. It says it may have up to 30 ppm of "heavy metals". (That's 30 parts of heavy metal per million of KOH, NOT 30 ppm in your solution) Sodium and Carbonate will be your major contaminates. Considering the very small amount of KOH you'll be using I doubt it will cause any problems. However, if you want to take the safe (paranoid?) route you could filter your solution through some carbon before using it.