OK, so I probably have too much light...

[dapellegrini]

I am just back from a week in CA and after the ritual PWC of the morning I noticed that I have some green spots on my glass and a few of my Crypt and Pennywort leaves... My Alternanthera Reineckii has always seemed to gather a bit of green algae on it's older leaves, as it grows very slow, but I have not had any real problems with it spreading, etc. Is this the same stuff?

Is this a high-light problem? Anyway of fixing it without taking away light, or is that the only real issue here? It is only on a few leaves. I have already scrubbed it off the glass.

Stats:

72g Freshwater Bowfront
Pressurized CO2 w/Regulator and Solenoid
SMS122 pH Monitor
Reactor 1000
Inline 300w Heater
2x Rena XP3 Canisters
324w HO T-5 Lighting (10k bulbs)

EI Dosing (KNO3, K2SO4 and Flourish Comprehensive)
Tap pH: ~8.0
pH After CO2 Injection: ~6.8
kH ~120ppm
gH ~200ppm
Temp: ~79F
Lights: 10 hours full blast (324watts) + 2 hours dusk/dawn (108watts)

I don't test much any more, so I am not sure on the other things, but they should be pretty close to the EI marks. Plants pearl from early afternoon until the lights go out every day.

TIA

 

[VaughnH]

Is 4.5 watts per gallon for a 72 gallon tank too much? My mind boggles! Seriously, I don't see that as "too much" light, but it is a light level that allows you no room at all to make mistakes. A bit too little CO2 - algae. A bit too much dead plant matter - algae. A bit too little phosphate - algae. A bit too much fish food - algae. Etc. I suggest the noon blast of 324 watts last only an hour. And, the rest of the 8 hours, not 10 hours, consist of about 216 watts or less.

 

[dapellegrini]

Well, I thought by using T5's that I was supposed to mulitply the standard WPG rule by something like 1.7... Which would give me >7.6 WPG.

I have never had to dose Phosphates, as typical feeding seemed to keep my level about right... The tank is realitively clean of mulm, etc... Hmmmm.... I will run some test tomorrow to see where things are at.

What causes this kind of algae?

 

[PeterGwee]

Seems like lack of PO4 is holding back the tank in terms of plant growth and the green spot algae indicates that as well. I'll suggest you dose it since the inorganic stuff we add never induce algae. Once you add the PO4, the uptake for the nutrients and CO2 should increase over time depending on how badly the plants are stunted. Then, be obessed with CO2 since when uptake increases, the levels might go south.

Regards
Peter Gwee

 

[dapellegrini]

Peter, The tank is very healthy overall. I have not dosed Phosphate as my test always shows more than 1 (whatever the measurement is) in the tank, which I assume is from feeding. I do have some Mono Potasium Phospahte (a couple lbs) but I was worried that adding any would be a bad thing. How much of this stuff should I be adding?

The tank before a very large trimming and the removal of a bunch of (too) fast growers:

The tank just after (yesterday):

Everything is growing at a nice pace, even the slow growers.

 

[reiverix]

I also run 6*54w T5s but on a 75g, so not much difference on our setups. I do run a very different light cycle from you though. Also, my lights are raised 10 inches above the water line so it's not so intense at the top (and I can get into the tank easy for pruning).

Two of my bulbs are on for 11 hours. Full blast for 6 hours. I honestly believe I could get away with 4 hours on full lighting and not see any adverse effects on the plants. If you think about light hungry plants in their natural environment, how many hours of full sunlight do they actually get? The hours around midday are probably the most intense but during the other hours, the sun is rising and setting.

PO4 out of my tap is always > 1ppm but I still add KH2PO4 within the EI guidelines. Green spot isn't a problem, even on the glass.

 

[dapellegrini]

Interesting reiverix. I will try adding some KH2PO4 today after I run some test. I have not had any spot algae problems before, and hesitate calling what I have now a "problem" really. Just a few leaves on a couple plants and a little bit on the glass. I just don't want it to become a problem!

From what I have gathered, NO3 is best around or under 10ppm, but everything will remain stable within a large variance, as long as you avoid extreme amounts (>100ppm) and bottoming out. I understand K to be the same, or easier... Not sure about PO4 though. What kind of variance can I run in the tank without much risk?

 

[dapellegrini]

Sure enough, PO4 was between 0 and .25ppm. That is the lowest I have ever seen it. Just added a bit with today's NO3 and K dosing... A pinch or so (~ 1/8 tsp).

Are there any good reference sites / literature on controling this kind of algae? If I balance out my PO4 between 1-3ppm, do I still need to worry about the lighting cycle? Thanks VaughnH, Peter and reiverix.

 

[PeterGwee]

You can do the standard EI method dosing of 10ppm of NO3 (KNO3), 2ppm of PO4 (KH2PO4) and general trace mix of 5ml per 20-30gal (TMG, Flourish and etc.) 3x a week. Weekly large water changes of 50% or more to reset the tank to prevent nutrients from building up to toxic levels. Main focus is then on the CO2 which Tom mentions is always the cause of most algae issues.

Unless you are willing to make standard solutions to calibrate your test kits, I would not trust the results.

Regards
Peter Gwee

 

[dapellegrini]

I also dose K2SO4 for additional K... Do the 50% PWC every saturday and also dose KNO3 and Flourish Comprehensive. Inject CO2 to around 30-35ppm using an automated system. Until now my PO4 was naturally high (>1ppm), so I avoided dosing. Looks like that is starting to change, so I will add KH2PO4 to my routine.

Thanks for the help.

 

[reiverix]

I don't think there's anything wrong with your light cycle at all. In fact, I used the same lighting hours as you for a long time but experimented to see if I could get away with less. Heat is an issue in my small room with a high light planted tank and a reef just a few feet away.

Even with relatively high PO4 in my tap, I've made the mistake of holding out on dosing until midweek after the weekend water change. Sometimes it can catch you offguard with the amount that plants can pull out of the water. So I don't concern myself with higher than normal PO4 or NO3. I just add enough so I know it's always going to be there.