Extremely high Phosphorus Levels

[marinereef01]

I just recently got back my ICP test and as I thought, have high nutrients. What's concerning is the off the charts phosphorus levels:

Nitrate: 17.45 mg/l
Phosphorus: 688.4 µg/l
Phosphate: u.

Anyone know what could really cause this? I have fish only in my tank right now, about 100 gal. I feed the Crossover diet from Neptune systems (3 drum rotations x2 day). I've watched when it is fed and my fish literally gobble it up and act like they haven't eaten. So, nothing is wasted and the tank is stocked good but not overstocked. Skimmer always pulls a bunch of gunk out.

Salt mix is Red Sea (blue bucket), I have a carbon reactor, and dose the highest amount of recommended Red Sea N0304-X yet my nutrients are still off the charts.

I'm at a loss

 

[bertoni]

That's rather high, if accurate. If the reading is accurate, the tank is getting too much food, most likely. How quickly the fish eat the food is not important. Most of what goes in, comes back out. Have you tested the level with another kit?

 

[mcgyvr]

Its almost always overfeeding and/or leaching from the rock..
Cut feeding in half for a while and see how the numbers trend..

 

[dkeller_nc]

Actually guys, this isn't unexpected at all. The OP has a fish-only tank, and at least as far as we can tell from his post, is not running any sort of phosphate-capture media. His phosphate level is about 2 ppm - that's completely expected and normal for a fish-only tank that is seeing relatively normal water changes and the only other export means is a skimmer (but I guess we're not sure if there's a skimmer, since it's fish-only). His high nitrate numbers (17 ppm) confirm this. Generally speaking, no saltwater aquarium will keep low phosphate and nitrate numbers over a long term period without some means of phosphate export other than the skimmer.

OP: The first thing to decide is whether this is going to remain fish-only. If it is, a phosphate level of 2ppm is no big deal, though it might fuel a bit of algae growth. That would be a high for a reef tank, but not catastrophically so. Ditto for the nitrate. For fish, you'd want to keep the nitrate below about 30ppm - 50ppm. If you have, or intend to add, invertebrates, then the nitrate will need to be kept a good deal lower, perhaps with an upper limit of 10 ppm.

 

[mcgyvr]

Actually guys, this isn't unexpected at all.

No one said it wasn't

Overfeeding/Overstocking/Lacking sufficient export means and or methods is VERY common..
Seems less common than it was 10 years ago but still very common today..

 

[dkeller_nc]

No, what I'm getting at is that you will STILL arrive at numbers like that from appropriate feeding, it will just take longer. In the end, just a skimmer for export isn't going to do it. So one must apply another, more efficient means of export. One's carbon dosing, which in effect uses the skimmer and/or mechanical filtration. A related method is carbon dosing via biopellets and/or a sulfur nitrate reactor.

Another's a direct chemical adsorption/precipitation method, such as GFO, lanthanum chloride or aluminum absorbants, although this only works on phosphates, of course. Yet another is massive water changes, though most of us choose not to do that for obvious reasons.

 

[mcgyvr]

No, what I'm getting at is that you will STILL arrive at numbers like that from appropriate feeding, it will just take longer. In the end, just a skimmer for export isn't going to do it. So one must apply another, more efficient means of export. One's carbon dosing, which in effect uses the skimmer and/or mechanical filtration. A related method is carbon dosing via biopellets and/or a sulfur nitrate reactor.

Another's a direct chemical adsorption/precipitation method, such as GFO, lanthanum chloride or aluminum absorbants, although this only works on phosphates, of course. Yet another is massive water changes, though most of us choose not to do that for obvious reasons.

I understand what you are getting at.. but don't think rising phosphate is an absolute as I feel that one can have continuously low nutrient levels without resorting to these "additional" export means like skimmers/fuges/carbon dosing,etc....

For me personally I have always maintained lower bioloads, avoided overfeeding, skimmed very lightly (empty cup once a month now if that) and only typically carbon dose for the first year as after that its not needed and I rarely if ever do water changes (I think I've done 2 x 10G in 2 years now on an 80G +40G sump).. I have never used GFO or other absorbing products either..
I have never (15+ years of tanks) had phosphates above .08ppm and my nitrates are in the 1-2ppm level..

I have found that bacterial populations do most of the work and I do as much as I can to encourage their growth/health..

I think the key is lower bioloads and I am likely "underfeeding" but my fish have always shown what I consider normal/acceptable growth..

Just throwing in my @0.02 as I feel that nutrient levels can be maintained long term with little more than the bacteria in the tank and proper feeding/stocking levels.. Nutrients don't have to creep up over time.. But yes it certainly happens with many..

 

[dkeller_nc]

Yeah, but you've noted a key thing - carbon dosing in the beginning. From the standpoint of phosphate (unlike nitrate), there are only 4 means of it leaving the aquarium. Algae growth that is harvested (either purposely as in a refugium, or cleaning it off of the rocks when the tank gets overgrown!), bacterial replication and removal, typically by a skimmer, water changes, and adsorption to chemical media.

And since phosphate is continuously added in the form of food, the relevant equation from classical mass balance to examine is "in - out = accumulation". Accumulation in the case of this equation can be either positive or negative, or at least in theory, zero. You certainly can reduce the "in" part to a somewhat lower rate, but it cannot, by definition, be zero, presuming one is keeping livestock that requires feeding. So by implication of the mass balance equation, and since the mathematical sign of the "in" part must always be positive, then to prevent a positive accumulation, the magnitude of "out" must at least equal the magnitude of "in".

If you examine the phosphate content of fish food, you find that the magnitude of "in" is relatively high. Typically, for frozen fish foods that are largely composed of fish, shellfish and crustaceans, a good average value for the phosphate content is going to be around 30 milligrams for every 10 grams of wet weight. If we assume that there's a reasonable amount of fish in a 100 gallon tank, and they're fed 10 grams of food per day, that would mean adding 0.3 ppm of phosphate to the tank per day.

That would be very difficult to overcome with water changes alone, so employing one or more of the other 3 export mechanisms listed above would be desirable. Overall, what I'm pointing out is that one cannot necessarily conclude that a fish-only tank with high phosphate and/or nitrate concentrations is overstocked and/or overfed. It depends on how fast those water parameters have risen to those levels and whether any export methods are being carried out by the aquarist, either intentionally or unintentionally.

 

[Khazmodain]

I have found that bacterial populations do most of the work and I do as much as I can to encourage their growth/health..

+1 ^This.

 

[Jonesrd1]

Why phosphorus and no posphate? It is possible but highly unlikely that all of the dissolved P is in the form of TP. Is it possible that this is an analytical error? That would be my SWAG. Ron