How do you lower phosphates when nitrates are 0?

[joelespinoza]

I am curious how everyone here lowers phosphates when their nitrates reach zero. Do you use GFO or add nitrates to the tank somehow? Possibly drip a small amount of ammonia into the sump? I am looking for a cheap way to get P down a bit.

I am still not 100% sure my problem is P, but I never have nitrates and my DT grows quite a bit of brownish looking algae on the glass, I am starting to get some bubble algae sprouting up on the rocks, and my coraline growth is minimal even though my alk/cal/mag numbers look great. It is possible that either my scrubber is not powerful enough (quite possible and have upgrades on the way) or that I have some phosphate in my water.

Anyway, if there is a cheap method to lower phosphates a bit I figure it would be cheaper to try that then to buy a test kit for them. What do you guys think of putting a few drops of ammonia into the sump?

[kerry]

You really need to know if your phos is elevated. No since in experimenting on your tank if there is no need to. API has a cheap Phos kit. It might not be the most accurate kit but at least you would have an idea. I would say NO to the ammonia!!!

[joelespinoza]

Here are some pics of what I am dealing with, I scrubbed the front glass completely clean 6 days ago:

Front of the glass:
http://i18.photobucket.com/albums/b124/JoelEspinoza/PICT0057Medium.jpg

Through algae covered glass to rocks with almost 0 coraline growth:
http://i18.photobucket.com/albums/b124/JoelEspinoza/PICT0053Medium.jpg

http://i18.photobucket.com/albums/b124/JoelEspinoza/PICT0046Medium.jpg

http://i18.photobucket.com/albums/b124/JoelEspinoza/PICT0054Medium.jpg

http://i18.photobucket.com/albums/b124/JoelEspinoza/PICT0048Medium.jpg

http://i18.photobucket.com/albums/b124/JoelEspinoza/PICT0050Medium.jpg

Bubble algae:

http://i18.photobucket.com/albums/b124/JoelEspinoza/PICT0052Medium.jpg

Full tank:
http://i18.photobucket.com/albums/b124/JoelEspinoza/PICT0056Medium.jpg

[SantaMonica]

Nitrate is never zero. If you want to prove that to yourself, get a low-range N kit, not the high-range one that everyone uses. It it were zero, you would not have algae in the tank.

Every bit of food, pee (especially) and poop that goes into the water adds N.

You don't need to add anything to make it happen.

[Floyd R Turbo]

Here's where I'm going to disagree because for a very long time I have tested rock-bottom zero N on Salifert looking through the side and still have P. With that much live rock, you will have a decent amount of naturally occuring denitrification occurring that will cause N to bottom out and the scrubber will stop taking up the excess P. I have encountered this personally as have many others on this forum. The additional denitrification mechanism without an additional phosphate removal mechanism means your P will rise.

Adding a very small amount of GFO in a decent flow location will help keep P in check, as long as you don't use too much to the point where it's pulling all of it out completely and then limiting P causing N to rise.

As far as P test kits go, IMO they're all worthless when you look at the visible kits (API, Salifert, etc) because the range just gets too low to give you any useful information. Get the Hanna Phosphate Checker and make sure to order extra reagent packs, and follow the instructions properly.

[joelespinoza]

With that much live rock, you will have a decent amount of naturally occuring denitrification occurring that will cause N to bottom out and the scrubber will stop taking up the excess P. I have encountered this personally as have many others on this forum. The additional denitrification mechanism without an additional phosphate removal mechanism means your P will rise.

Yea, I think this might be what I am experiencing.


As far as P test kits go, IMO they're all worthless when you look at the visible kits (API, Salifert, etc) because the range just gets too low to give you any useful information. Get the Hanna Phosphate Checker and make sure to order extra reagent packs, and follow the instructions properly.

Yea, I am a bit unwilling to spend money on a questionable test kit, and I dont have the budget for the Hanna one, I think it would be easier to experimentally lower P by a small amount and observe the results.


You really need to know if your phos is elevated. No since in experimenting on your tank if there is no need to. API has a cheap Phos kit. It might not be the most accurate kit but at least you would have an idea. I would say NO to the ammonia!!!

That kit apparently would not tell me anything, and out of curiosity, why are you so opposed to adding a SMALL (a couple drops at most in a day) amount of ammonia to the sump? I would rather add pure nitrate, but its not as easy to come by. I guess I could add CO(NH2)2, which would probably be less toxic and it is easy to come by =).

[Floyd R Turbo]

http://www.aquariumfertilizer.com/index.asp?Option1=inven&EditU=2&Regit=3

[kerry]

Ammonia is way to deadly, I vote for Floyds link for the fert.

[SantaMonica]

If you want to add anything to the water, just add food.

[joelespinoza]

If you want to add anything to the water, just add food.

But wont food add phosphates and nitrates?

[Floyd R Turbo]

Yes, in the same ratio that they are taken up by the algae. This is the heart of the issue. Unless your food is seeded with the perfect amount of N to offset the amount taken up by natural denitrification, you will end up continuing to increase P, at least to some level. Mine seems to plateau out around 0.16, I've never seen it above that but also never seen it below 0.05

[srusso]

Agreed, I have a rather "underpowered" scrubber. Almost two years (little to no water changes) I had a build up of P. I contribute it to that fact that the food we all feed has a ton of P in it. Took Floyd's advice got a hanna and tested at .31

Been passively using GFO for a few weeks now and I test between .07 and .16
I maybe be buying a reactor to see if actively running GFO would drop it further.

[joelespinoza]

I will try to get a Hanna checker later on when I can afford one, for right now do you guys have a brand of inexpensive GFO you have had good success with?

[herring_fish]

Just want to confirm the live rock denitrification. I have an often repeated the story about an added sump that was full of crush coral. When I hooked it up, the N fell and my scrubber stopped working so P went up. My N was so low that I didn't get hair algae in the tank but P stayed high so I am disconnecting it.

I am surprised though. In the old day of scrubbing, everyone had as much live rock as you do and everything was fine. Is you scrubber indeed too small or does in have too little light on it?

GFO should work fine but I'd hate to have to futz around with that stuff if you are just under powered.

[CHOMPERS]

I have already done this experiment and dosing ammonia can be done safely. I have dosed with ammonia for this same problem. I used a medical peristalistic dosing pump to meter it into the DT's overflow. This is a direct route to the ATS. My ATS is fed from two sides and the light bulbs run horizontally so cover both screens evenly. To determine if the ATS has single pass efficiency, I dosed only one side and compared the growth of the two sides after one week. The non-dosed side did not have any extra growth but the dosed side did. I repeated the experiment for two more weeks and had the same results each time. I then switched sides with the dosing and had extra growth on that side and the other side returned to normal.

I have a 150g DT and I dosed four drops of ammonia per day. The ammonia was diluted into 100ml of water and dosed countinuously though out the day. I have taken water samples from below the ATS and all tested zero for ammonia. The ammonia dose was derived from someone elses experiences with cycling tanks by ammonia dosing (the dose may be increased or decreased depending on ATS size and maturity).

http://i1186.photobucket.com/albums/z362/MorkOrk/12161808.jpg

[herring_fish]

Wow very nice to know.