Brown Spots On Leaves

[Blondielovesfish]

My blue hygrophila (hygrophila corymbosa) has recently started developing brown spots in its leaves. I've had it for almost a month and it has started doing this in the last week or so.
Brief research has led me to believe it might be caused by a deficiency of iron, however I can't seem to find if this is the exact cause.
 
I don't currently dose with any ferts (any you can recommend?) and my lighting is moderate. I have an 11w AquaOne PL sunlight tube and its a 22L tank.
 
Here's a pic in which you can see the spots (sorry for the poor quality, it was taken on my phone).

 
 
What is wrong and what can I do to stop it?
 
Thank you

 

[three-fingers]

It's hard to tell from the pic, I think I see holes more than brown spots? Either way, H. corymbosa is a fast growing species, so as as you were thinking, it could be a deficiency in some micronutrient

.
 
Not sure what brands are available to you in NZ, but a very good off the shelf fertiliser is Seachem Flourish, it has the most comprehensive ingredient list I know of, and uses iron gluconate instead of normal chelated iron - which means it's suited for feeding plants over a wider variety of water conditions compared to other brands. However if your selection is limited, nearly any aquatic fertiliser should help as they will provide the most important micronutrients.  Some are just less comprehensive and far more diluted, I usually recommend people make their own to save money, but economy probably isn't an issue on a 22l tank

.
 
The only one I would generally avoid is API Leaf Zone as it's missing a lot of nutrients that plants use.

 

[Tongue_Flicker]

Kinda blurry but it looks like it may have been caused by a diatom, some brown algae infestation or a plant virus. Have you tried snipping the infected leaves to see if new leaves get infected?

 

[Blondielovesfish]

Thanks for the reply.
 
Yes, they are indeed holes, sorry, I thought I had included that in the original post but see now that i didn't sorry.
 
Thanks for that, I think I will get the flourish and see if the plants condition improve. Will the flourish have any side effects on the vallis I have in the tank? (i.e. causes it to melt?).

 

[eaglesaquarium]

No.  You are thinking of 'Flourish Excel'.  Be sure not to buy that.  That's is a 'liquid carbon' product and it can cause vallisneria to melt.

 

[Blondielovesfish]

Yeah, I know they're different, was just making sure it doesn't have the same effect.
 
Thank you

 

[ian]

This is a c02 deficiency.

 

[Blondielovesfish]

This is a c02 deficiency.

 
Ugh, really? TBH the last thing I want to do is be messing around with CO2 reactors. 
I've bought some flourish and added it to the tank, so fingers crossed it will help, if not then I suppose I'll have to get into the world of CO2, either that or just rip the plants out.

 

[eaglesaquarium]

Excel would be something else to try, but that won't be something that the vals like.

 

[three-fingers]

Agreed it could be CO2 issues too, especially when I went back and read that its an 11w bent T5 tube over a 22L tank (this is a lot of light). Holes in the leaves coukd also suggests potassium deficiency (in Flourish) to me, and in the pic parts of those leaves look pale as well.
 
Personally I don't like liquid carbon much, but one way to improve CO2 availability would be to reduce light intensity, rather than add CO2, since this will reduce the plants nutrient demands. Reducing light intensity would also reduce other nutrient demands, so its definitely worth trying if its an option. You could put some sort of diffuser under the light to reduce the intensity, or add floating plants.
 
Micro fertilisers cant hurt and will probably help a little bit even if it is mainly a CO2 problem .

 

[Blondielovesfish]

Okay, I will look at diffusing the light, any suggestions on how to do that?

 

[eaglesaquarium]

The easiest way in some cases is to raise the light a few more inches above the water surface -
 
Intensity is related to the inverse square of the distance... meaning if you double the distance of the light source, you end up with 1/4 the intensity.

 

[daizeUK]

Reducing light duration may be easier than reducing intensity.

 

[eaglesaquarium]

Well, reducing the intensity is more important than duration, because its about the 'rate' of use, not just the total used.
 
If the CO2 is used up too fast based on the intensity of the light, then it will still be used up with a shorter duration.  However reducing the intensity will decrease the CO2 demand for the plants and allows the natural diffusion rate of CO2 back into the water to better handle the use by the plants, as the CO2 can only diffuse into tank so quickly without injection through either pressurized or biological means.  So, the rate of use is the bigger concern, IMHO.

 

[three-fingers]

Okay, I will look at diffusing the light, any suggestions on how to do that?

If possible, increase light height as Eaglesaquarium recommends, or place some frosted glass/tinted plastic between the light and the waters surface. 
 
Another option I've seen people use is to partially cover the bulb cover with evenly spaced out strips of electrical tape, however I personally don't feel safe recommending this due to fire risk, especially on a T5HO bulb! Though thinking of this may give you some food for thought .