A question - Low NO3- and nonexistant Phosphate

[W_Oz]

So I find myself in a new situation. I have low nitrate (0.9ppm) and zero phosphate (phosphate detection limit .005ppm), pH= 7.47, lights are back to a 10 hour cycle and the green buggers are doing something I've never seen before. I have algae covering the water surface of the tank. Bearing in mind this tank is planted, what's the deal? They can't be getting light from the window (or can they?) since that's above the waterline and I have a cabinet top on the tank so the only light they should be getting is either from the aquarium lights themselves or refracted window light.

The surface algae "goes away" when I do water changes as the water level gets low enough to allow the power heads and canister discharges to disturb the water but two or three days later its back and if I let it go for more than 4 days the stuff will cause the surface to appear to be stagnant.

Other info - 55gal. semiweekly water changes ~15% and 136 Watts of 6500-6700K lighting.

I'd like to add some more plants to this tank, though I'm concerned about needing to dose with Nitrates/Phosphates at this point (I didn't know my levels were quite that low) and I don't really want to have to worry about CO2 injection either.

[Lady Hobbs]

How much surface bubbles do you have?

[ILuvMyGoldBarb]

Sounds like you've actually gone too far towards minimizing surface movement. You need that surface movement in the tank. If you can increase the surface movement then I highly suspect you won't have much of a problem.

[kaybee]

W_Oz, just a question here, what po4 test kit or instrument are you using? I'd be interested in using one which could test as low as 0.005ppm phosphate.

[W_Oz]

W_Oz, just a question here, what po4 test kit or instrument are you using? I'd be interested in using one which could test as low as 0.005ppm phosphate.
It's an analytical Ion Chromatograph. (the column alone costs us a couple grand)

The tank itself sees virtually zero surface agitation. All of the equipment is setup around 4" below the high water line of the tank. I'll take the canister discharge and point it towards the surface a little more or grab the spray bar on the smaller canister and set that up to stir up the top a bit more.

I've been curious about the Dissolved Oxygen content of the tank and I'll be taking a sample in to work on Sunday to see what the DO meter says about that. But, without CO2 injection I'm concerned about the poor plants.

[smaug]

It's an analytical Ion Chromatograph. (the column alone costs us a couple grand)

The tank itself sees virtually zero surface agitation. All of the equipment is setup around 4" below the high water line of the tank. I'll take the canister discharge and point it toward the surface a little more or grab the spray bar on the smaller canister and set that up to stir up the top a bit more.

I've been curious about the Dissolved Oxygen content of the tank and I'll be taking a sample in to work on Sunday to see what the DO meter says about that. But, without CO2 injection I'm concerned about the poor plants.
co2 injection isn't near as necessary as is talked about.Ive gone without it for years.I do use seachem excel though.Get an airpump and run it at night,it will help break down any nastys which accumulate during the day.Pointing the outlet toward the surface is a good idea as well.

[ILuvMyGoldBarb]

That lack of surface aggitation is not only going to cause the algae but starve your plants and fish of Oxygen. The Oxygen level has to be low in that tank.

[Evil Slimy]

I also agree on the surface agitation issue. Even in co2 injected tanks, you don't want to break the surface, but you still want some ripples and movement. If you are not injecting co2 there's no point in limiting surface agitation.
I don't know how many plants you have, but if you end up with other algae issues later, it could also be that your nutrient levels are too low. These are target levels recommended for E.I. dosing in a planted tank:
* Nitrates 10-20ppm
* Phosphates 1.0-2.0 ppm
* Iron 0.1-1.0 ppm
* Potassium 10-20 ppm

[W_Oz]

So...
Get more surface agitation going, check.

Increase nutrient levels (N-P-K).... By... what?
Dosing or adding Bioload?

Plants, well.

There are several (6 or 7) Java ferns here an there, two Amazon Swords (one throwing off runners like mad the other just seems to be doing fine), a few crypts, some sort of Val that I was given from a friend with a couple daughter plants, a micro sword clump, and Java moss on a rock and the starting of a moss wall (which is going to take a year and a half to fill in lol) started with some of the trimmings off of the overgrown rock.

[Evil Slimy]

Lack of surface movement could cause the surface algae. What he is describing sound like surface scum like this (http://aquariumalgae.blogspot.com/2007/06/as-we-can-see-in-this-article-algae.html).

For nutrients I would definitely dose instead of adding bioload. If you are dosing you have direct control over it and can raise or lower nutrients level as needed. For example, in my case I have to up the phosphates dose to keep green spot algae away. If you have low light you can start with half of the suggested target levels and then adjust depending on how your tank does.

[W_Oz]

That looks exactly like what I've go going actually. I'll stop in to the LFS and buy some NPK.

I've had to setup a hospital tank (unrelated subject) thanks to a Bala who's gone and banged himself up pretty badly a couple days ago when he got spooked as my gf and I entered the room and appears to have a form of "pop-eye" with what appears to be a cataract on one of his eyes and a chunked lip. After he's better I'm heavily leaning towards selling them locally to a better home (read larger tank) and restocking with some danios or something similar.

[W_Oz]

Welp, that problem's cleared right up, the plants are growing and algae is looking to be on the run. On another note, Cyano has started appearing, ugh... lol things just keep getting better :c2: