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Tom -- The difference in densities don't matter too much with the assumptions we are making (580 kg versus 565) and 500 kg is great for easy math. Great point about the PO4 percentage -- change made below to double the concentration. The calculator allows for different concentrations of stock solution. Alan -- Another good point about dosing. Maybe I am being too conservative, and he definitely won't see the change on the normal meter. But we may want to start slow and just add increasing doses of K2HPO4, if needed. I worry about dumping in a lot of phosphate and causing an algal bloom. If the theory is right, then he'll probably observe lowering nitrate levels before seeing phosphate levels rise. I'll leave it to discussion -- is this too conservative? ================================ OK -- let's crowd source this to make sure my math is right. Your tank is 200 gallons. Let's be conservative and say that the rock and equipment displaces 50 gallons, leaving 150 gallons of water. 1) 150 gallons equals 567 kilograms of water. Math check: 1 gallon = 3.78 liters 150 gallons = 567 liters since water has a density of 1 kilogram/liter 150 gallons = 567 kilograms of water Let's round down to 500 kilograms for ease. According to Holmes-Farley, reef tank phosphates concentration should be less than 0.03 ppm (milligrams phosphate/kilogram water). I propose that you add 0.01 ppm phosphate per dose. This increase should be detectable using phosphate test kits, but not exceed recommended amounts. Now, how much K2HPO4 do you need to add to raise phosphate levels by 0.01 ppm? Adding 5 milligrams of K2HPO4 to 500 kilograms of water will increase the K2HPO4 concentration by 0.010 ppm. Math check: 500 milligrams HPO4 / 500 kilograms = 1 milligram/kilogram = 1 ppm 5 milligrams HPO4 / 500 kilograms = 0.01 milligram/kilogram = 0.01 ppm OK, now we need to make the stock K2HPO4 solution. We want to dose as little volume as possible. I propose dosing 10 mg of K2HPO4 (10 milligrams of K2HPO4 * 55% ~= 5 milligrams HPO4)in 1 milliliter, initially. That means that you should dissolve 10 grams of K2HPO4 into 1 liter (1 kilogram) of RO/DI water. Math check: 10 grams K2HPO4 / 1 liter of water = 10 milligrams K2HPO4 / 1 milliliter of water ~= 5 milligrams HPO4(incidentally, 5 grams / kilogram = 5 ppt) How does that look? Dosing procedure: 1) Measure phosphates and nitrates daily at the same time of day. 2) After measurement, add 1 milliliter of the K2HPO4 stock into the sump. 3) Wait about 10 minutes and measure phosphate levels again to note change. 4) If no change in phosphate levels, then wait until the next day to add another dose (after measuring phosphates and nitrates). This is the most likely scenario because I was conservative in my assumptions. 5) If phosphate levels do increase after the dose, then do not dose again until phosphate levels fall below detection. This will give the biopellets and cheato time to work. We can think about the trending test results together. We are shooting for the N:P ratio of about 20:1. Except for increasing flow on the chaeto (can there be too much flow on chaeto? Not sure.), I would keep everything else the same for now. I would also be prepared to test nitrate and phosphate daily. After adding a single dose of phosphate, it is critical to monitor your levels over time to see what happens. I would also be sure to have a water change ready to go in case of emergency. Jeff

OK -- let's crowd source this to make sure my math is right. Your tank is 200 gallons. Let's be conservative and say that the rock and equipment displaces 50 gallons, leaving 150 gallons of water. 1) 150 gallons equals 567 kilograms of water. Math check: 1 gallon = 3.78 liters 150 gallons = 567 liters since water has a density of 1 kilogram/liter 150 gallons = 567 kilograms of water Let's round down to 500 kilograms for ease. According to Holmes-Farley, reef tank phosphates concentration should be less than 0.03 ppm (milligrams phosphate/kilogram water). I propose that you add 0.01 ppm phosphate per dose. This increase should be detectable using phosphate test kits, but not exceed recommended amounts. Now, how much K2HPO4 do you need to add to raise phosphate levels by 0.01 ppm? Adding 5 milligrams of K2HPO4 to 500 kilograms of water will increase the K2HPO4 concentration by 0.010 ppm. Math check: 500 milligrams/500 kilograms = 1 milligram/kilogram = 1 ppm 5 milligrams/500 kilograms = 0.01 milligram/kilogram = 0.01 ppm OK, now we need to make the stock K2HPO4 solution. We want to dose as little volume as possible. I propose dosing 5 mg of K2HPO4 in 1 milliliter. That means that you should dissolve 5 grams of K2HPO4 into 1 liter (1 kilogram) of RO/DI water. Math check: 5 grams K2HPO4 / 1 liter of water = 5 milligrams K2HPO4 / 1 milliliter of water (incidentally, 5 grams / kilogram = 5 ppt) How does that look? Dosing procedure: 1) Measure phosphates and nitrates daily at the same time of day. 2) After measurement, add 1 milliliter of the K2HPO4 stock into the sump. 3) Wait about 10 minutes and measure phosphate levels again to note change. 4) If no change in phosphate levels, then wait until the next day to add another dose (after measuring phosphates and nitrates). This is the most likely scenario because I was conservative in my assumptions. 5) If phosphate levels do increase after the dose, then do not dose again until phosphate levels fall below detection. This will give the biopellets and cheato time to work. We can think about the trending test results together. We are shooting for the N:P ratio of about 20:1. Except for increasing flow on the chaeto (can there be too much flow on chaeto? Not sure.), I would keep everything else the same for now. I would also be prepared to test nitrate and phosphate daily. After adding a single dose of phosphate, it is critical to monitor your levels over time to see what happens. I would also be sure to have a water change ready to go in case of emergency. Jeff

http://www.advancedaquarist.com/blog/fish-poop-is-great-coral-food Neat article on the ratio of nutrients.

I think he has enough flora in the tank right now. They will start multiplying and growing once things get into balance.

Anytime. You can PM or we can work it out here when you are ready to go. Do you have a weighing scale? If so does it read in metric or conventional? I would optimize/increase the flow through chaeto before messing with the lights.

LOL The only thing I can think of is that there is a ton of bacteria growth and that growth is limited by phosphorous. But that would typically lead to lower levels of nitrate -- <10ppm. I have no idea where the excess nitrate came from so early in the tank's history. My guess is that the slightest addition of phosphorous would like to a growth explosion -- so it would be best to harness it in the chaeto and biopellets.

So if it were my tank... I'd have to consider the Redfield ratio (which is just one of many, but the underlying principle is the same). Thinking with my chemistry PhD hat, I'd go with Tom's suggestion and slowly add in some dipotassium phosphate. It is food safe and water soluble. Amazon has some for sale (http://www.amazon.com/Potassium-Phosphate-Dibasic-Grade-1000g/dp/B00CF28K2G/ref=sr_1_1?ie=UTF8&qid=1400181607&sr=8-1&keywords=potassium+phosphate) and for more info: http://en.wikipedia.org/wiki/Dipotassium_phosphate I would make a 1 part per thousand solution. So that is 1 g of solid to 1 kg (1 liter) of water. If you are serious about doing this, I'll help you think about it. While adding phosphate.. I'd be sure that my biopellets were perfect. Nice flow, no build up... etc. I'd also make sure that the chaeto is good to go. Optimal light and flow (like sen5241b wrote). In theory, the phosphates will not increase and the nitrates will decrease. Once the system has balanced then phosphate dosing is stopped. Then I'd to work to maintain low levels by increasing flow to remove detrital build ups, maybe remove corals that hate flow and the sand.

That is correct. Chaeto, other algae, and bacteria consume more phosphate then coral.

I agree in principle with a build up of detritus and/or stocking levels as a contributor. But detritus and excess waste would raise nitrates and phosphates. Not just nitrates alone. I'd hazard to say that it is more common to have excess phosphate. But excess nitrate and low phosphate is the head scratcher for me.

True points -- but you still need phosphate. The tank in question is phosphate starved.

Oh, I see what you mean -- for corrosion control. During peak farming seasons, when farmers fertilize, the unintentional nitrates and phosphates in the Potomac jump to high concentrations.

Another thought, what about removing the SPS coral and adding more dirty water tolerant coral?

You'll get a ton of nitrates too.

^^^^^ This. In a larger point, aside from having a high nitrate number, what is going wrong with the tank that you want to fix? Are corals dying or not growing to your satisfaction?

The rule of thumb is to feed the photosynthetic Cnidarian based on the size of its mouth (e.g. Larger LPS like lobophyllia will benefit from target feeding.) With that in mind, most corals absorb their supplemental nutrition from the water. In nature, that can eat microplankton, but that's not readily available in our tanks. Most tanks do fine with just the fish poop and dissolved nutrients that come from fish food. If you do want to feed your coral because you want faster growth or maybe more color, I suggest a suspension food, like Marine Snow or Red Sea's Reef Energy, but every company makes a variant. I'm using Red Sea currently because when I add it, I observe significant polyp extension -- which is visually appealing. If you broadcast feed your coral keep a close eye on your N's and P's and adjust the feeding accordingly.

Neato -- it may be a bit cheap but if you are looking for a pop-up for an emergency this could do the trick! Thanks for sharing!

I had a stowaway tiger goby from my Tampa Bay Saltwater order. Fun!! Great fish -- lots of personality.

http://www.orafarm.com/products/fish/gobies/tiger/ Tiger Goby?

Sorry about your loss. A fish once died in my rock work. I got him out using a small baster. The suction on his side was able to lift him out.

Man o man! Must be so awesome to dose some nature into your tank.

It could be both in a feed back loop. I would normally advocate for a water change. It is always the simplest solution. The problem here is that Rob is working on a 300 gallon tank. A 50% change is a 150 gallon change and that sounds impracticable, let alone more than that. I want to be clear that my suggestion is not that the water is too clean (obviously it is not). My suggestion is that there is too much competition for limited resources. And the LPS are losing. I think of it as bringing 10 cupcakes when there are a dozen people at the party. Two people are going to lose out on a delicious cupcake. More so if someone is big jerk and eats two. This is like Rob's tank since there are a lot of fish and a lot of food is introduced into the system. Saying the water is too clean is saying that no one brought cupcakes at all. This is a system where food is purposely withheld (some people feed once a week) and skimming, water changes, and biopellets/dosing are all aggressive.

Flora is the general word for non-animal life. So the flora on the rocks work out the N cycle. The Flora on the biopellets consume NO3 and PO4. The Flora allow your fish and coral (the fauna) to survive. We use Flora because there are many different types of bacteria in our tanks. And bacteria tank from tank to tank vary. So we can just say flora to simplify. Metabolites are to bacteria as feces and urine are to fauna.

LOL There are close to 10k species of amphipod and their size can range from from 1 mm to that bohemoth pictured above. Paul is that a Long Island Sound collection?

Some light reading to help everyone. http://books.google.com/books?id=SX5hw1JnNV4C&pg=PT124&dq=great+barrier+reef+7.+primary+production&hl=en&sa=X&ei=B3FlU7jPEbStsATnxYGQBA&ved=0CDgQ6AEwAA#v=onepage&q=great%20barrier%20reef%207.%20primary%20production&f=false

The biopellets would certainly contribute to a situation where nutrients are being removed faster than the LPS can use them. The bacteria on the biopellets are competing with the LPS (and other coral and algae) for limited nutrient resources. We always think about nitrate and phosphate because that is what we measure. But life cannot live on nitrate and phosphate alone and they are certainly not the only nutrients available in our tank water. In good cases, the bacteria on biopellets and from carbon dosing consume all the nutrients before nuisance algae can absorb them and grow wildly. So why can't that be the same scenario for some types of coral? In this case, the hypothesis is that the bacteria are winning and so the LPS are starving. Like a vine overgrowing a tree.