Sugar dosing only reduce nitrate but not phosphate

[wayne in norway]

I think the theory/practise is that by adding sugar you encourage the growth of bacteria that can then be skimmed out (usually you see a little cloudiness in the water when you start, dose or especially overdose) Removing those bacteria removes P, and the growth of new bacteria to replace those will further remove Pfrom the water column. Thus you get over the hurdle of them recycling rather then 'using' P.

[OliverM3]

Anyone add the sugar to their top off water?
I've debated on doing this but I was worried that the sugar may settle and accidentally overdose the tank.
So I've always added it manually.

It would be nice to just mix up the correct concentration of sugar water then just let it slowly mix in with your auto top off.

[m2434]

Wayne,
Good point, I think that is what Randy was saying in his article.
I think this is really facinating concept and sounds reasonable, but when I think about it, it just dosn't quite make sense.

If your primary source of phosphate is food, the food decays and the big biomolecules from the decaying matter are removed by the skimmer. If it is taken up by bacteria, the phosphate atoms would get absorbed and then, when the bacteria dies, would be released back into the water. This would again be in the form of big biomolecules, which would be removed by your protein skimmer.

So I don't see why the affinity of dead decaying bacteria to skimmate, would be any higher than the afinity of dead decaying food for skimmate. Either way the rate limiting step is the efficiency of your skimmer... There might be an initial decline as new bacterial growth occurs, but the baterial load will saturate and in the end unless you can remove it, the phosphates still there waiting to be released...

On the otherhand something like GFO or macroalgea is not limited in this way, because you can physically pull it out once and a while.

[Nem0]

m2434,

The difference is the improve efficiency of the skimmer. I notice that when I dose sugar, the skimmer goes "crazy" and I get 3x more skimmate than normal....and I'm not talking about clear water, but brown and disgusting skimmate. I would assume that it is the bacteria being skimmed out along with the nitrate and Po4 that built part of the molecule.

I'm even contemplating whether I should do this regularly on a lower dosage (like in the top off water OliverM3 suggested) and permanently improve the efficiency of my skimmer.

[m2434]

Cool! regardless of whats happening, if you can get you skimmer to work better there's something to be said for it.

[jacmyoung]

True, after sugar addition, bacteria bloom will be so quick the skimmer goes crazy, removing the bacteria mass. So if the bacteria do take up P, P is then removed by the skimmer before having the chance to be recycled.

If your P stays at 1ppm and not going up, and you have no algae issue, then why worry?

My tank has four fish, I feed once a day. Never had water change in the past 18 months, top off is done with tap water, nitrate is kept under 10ppm with sugar addition once every few days, no algae problem so never bothered to check P level. Though I have always wondered what my P level really is.

In a few months I plan to introduce coral, I will start checking P as a precaution.

[wayne in norway]

I am no expert on the how skimmers would pick up live bacteria, but my assumption is that the live bacteria (with P) are skimmed out. The last stage of my recent algae war was a colossal bacterial bloom presumably as I had mass die off of algae, and it skimmed straight out as caramel coloured (but not flavoured ) skimmate compared to my normal green/brown. I can easily imagine 'sticky' bacteria sticking to air bubbles very well.

Sadly if your P is at 1 and not going up you still need to worry. Unlike nitrate, where the documented effects of elevated levels are a bit vague, elevated P has a direct, documented and detrimental effect on calcification in corals, and 1 is definitely in the range defined as 'elevated'. For healthy corals, it needs to be reduced else they might survive, but physically cannot grow.

[kidchill]

Yah, I agree with what's being said. If the bacteria have up-take and use the phos and then they're removed, then yes it's removed from the system, but my thought is still.....why not just use a phos binder and forget about all the extra mumbo-jumbo with the sugar? You can enough phos binder for 150g for like $10-20, granted sugar is cheaper, but then you're kinda throwing your ecosystem outta whack....Either way, as long as you get your phos and nitrates down it works...

m2434....are you available if I have some general chem questions for you? I'm in anesthesia school and had Gen Chem 1&2 like 3 years ago and we're starting to hit up some bio and organic chem now? If not, that's cool, it just seems like our instructors know more about the clinical use of drugs then their chemical properties and there's so much conflicting research and information in the anesthesia texts. I didn't think that they could screw with the laws of physics and chemistry, but I see different values and properties listed in the same book on different pages....It's crazy!!! So, if you can, awesome, if not, no problem I'll have to be a google-maniac!!

[m2434]

kidchill, you can PM me if realy you want. I'm not a chemist, I had a lot of chem as an undergrad, but that was more than 5 minutes ago...