Black Spots and Poor Root Growth on Amazon Frogbit (PICS)

HI guys!

I love Amazon Frogbit - this is my first time keeping it, and I'm having some issues. The five or so plants I purchased have multiplied vigorously over the last 3 weeks, but the new growth has smaller leaves (stunted?), and I'm also noticing black spots and eventual yellowing/decay of the leaves.

I have the plants in two 2 gallon tanks, for the time being I'll just describe the one that's doing worst:

TANK #1:

Size: 2 gal
Water Parameters: AM=0 NI=0 NA=0 (thanks, plants!)

Lighting:
Coralife 10,000 K 9 watt bulb 8" above water (have had this bulb for a while; it may need replacing)

Nutrients:
This is a bare bottom tank, it contains a small potted crypt (possibly a parva?) in about 1/4 cup of fluorite substrate (re-used from a previous tank, so may be depleted) with 1/4 of a root tab, I figured some of those nutrients are getting into the water column. The tank is also temporarily home to 5 (overfed) wildtype feeder guppies.

Notes on Other Plants in Tank: The potted crypt started out with tall leggy stems but lost these almost immediately after introduction and is now growing at about 1/3 its former height (apparently healthily). I also have a nice anubias coffeefolia in there - it was growing fast initially but has slowed and lost much of its reddish color on stems/shoots.

Filtration: DIY sponge filter... I have heard remarks about water on frogbit leaves, and the filter is pretty bubbly/splashy...could this be the source of my black spots?

Other Factors: I do notice that my guppies like to nibble the root hairs of the frogbit, some bits get a pretty thorough scouring or are completely chewed. I figure that if the plants were healthy they would be keeping up with this, though.

I did add salt recently (1tbsp/2 gal), which has since been diluted through water changes but have read that frogbit is tolerant, and did not notice any corresponding alterations in the plants.

Algae: None


Any thoughts on my situation?

I have ordered Flourish Complete to start dosing.



Thanks so much, guys!

 

Ok, so digging around some more in the stickies has revealed 2 things:

1) I need CO2 supplementation given the crazy 4.5 wats/gallon I have going on this little tank. Since I have no intention of doing actual CO2, I will get some Excel and hope my teeny fish don't react badly to it, as some people's have *worried*

2) My plants are exhibiting signs of like, nine different nutrient deficiencies. The Flourish Complete I ordered should help address that.

Does this sound correct to you guys??

Still no mention of/remedy for black spots...

 

Ok, so digging around some more in the stickies has revealed 2 things:

1) I need CO2 supplementation given the crazy 4.5 wats/gallon I have going on this little tank. Since I have no intention of doing actual CO2, I will get some Excel and hope my teeny fish don't react badly to it, as some people's have *worried*

2) My plants are exhibiting signs of like, nine different nutrient deficiencies. The Flourish Complete I ordered should help address that.

Does this sound correct to you guys??

Still no mention of/remedy for black spots...

I have Excel and Flourish and have had no ill effects from any of my fish, even when I had teeny tiny baby endlers so I'm thinking you'll be okay

 

I don't think that frogbit needs Excel. Because it is floating, it has access to air's CO2 (about 400 ppm), "aerial advantage" versus the submerged plants.

I keep frogbit in several tanks. It seems to prefer calm water surface, moderate light under a glass top (humid air above) and Potassium fertilizers.

I also noticed that it prefers crowding because it grows very slow if there are only few of them in the tank (it takes months to double in number) and grow fast in top of each other.

 

That's very reassuring, thanks!!!

 

I don't think that frogbit needs Excel. Because it is floating, it has access to air's CO2 (about 400 ppm), "aerial advantage" versus the submerged plants.

I keep frogbit in several tanks. It seems to prefer calm water surface, moderate light under a glass top (humid air above) and Potassium fertilizers.

I also noticed that it prefers crowding because it grows very slow if there are only few of them in the tank (it takes months to double in number) and grow fast in top of each other.

Interesting about the CO2, that makes sense! My other plants would probably appreciate Excell though.

Turns out the w/gal thing doesn't apply to small tanks, and the member who wrote the sticky on that subject has like 23 w going over a 2 gallon. Has anybody got a reliable method/guide for determining tank lighting for less than 50 gal?

 

Even with high surface movement from my HOB I find my Frogbit grows best with excel and flourish. This stuff is said to go through growth cycles so you could be seeing a slow spot in growth naturally. Also, I have had higher lighting burn leaves hence those dark spots.