Floating Plants In A Low-Light Tank?

[juhason]

I am starting to have an brown algae problem, and the main reason is excess nutrients, but my lighting is also a bit too low. I will be able to up the lights to about 80watts (in a 55 gallon) which is about 1.5 watts per gallon, which I've read is ideal for low light tanks. However, in order to quickly use up the excess nutrients, I would like to get plants such as water lettuce or giant duckweed. If I do get these plants, will I have to have even more wattage in order to compensate for the light it'll block or will my plants be ok? 

 

[Byron]

The first thing I must sort out is the matter of using watts as a guide to intensity.  Watts is simply the amount of energy (electricity) a particular bulb or tube uses to produce the light it emits.  It really has nothing to do with the intensity or brightness.  As a quick example, I use T8 lighting.  The 48-inch tubes over my three largest tanks used to use 40 watts, but today they are being made to use 32 watts, yet the light intensity is actually a bit better.  The watts per gallon guide had some merit back when all tubes were much the same, in the days of T12, but no longer.  Watts is only a guide to intensity when comparing identical bulbs/tubes; for example, a 13w 6500K GE CFL bulb will emit more light than a 10w 6500K GE CFL bulb.
 
This "brown algae" we need to identify.  If it easily comes off with your finger, it is likely diatoms.  If it does not easily come off but needs scraping, it is probably a form of brush algae.  Excess nutrients can cause either, but so can too few nutrients, or too much or too little light.  To sort this out, I need to know the lighting you have (be specific) and the plant species.  Also, are you adding any plant fertilizers?  How often are water changes, and what volume, and are you vacuuming into the substrate.  What is the fish load like?  And what is the GH of your source (presumably tap) water?  All these factor into the balance.
 
A final example...my 70g tank has the "brightest" light of all my tanks, with two 32w T8 tubes for roughly a watt per gallon.  It is covered with Water Lettuce and Frogbit, and thick with lower plants like chain swords and larger swords, and moss everywhere.  I have to limit the light to no more than seven hours daily, or algae increases.  It is all about the balance.
 
Byron.

 

[noobgamers]

ive found amazon frogbit does really well as long as you keep it still otherwise it just floats around the tank endlessly but i started with 3 pieces and now have a 60cm square section of the stuff
ive heard that water lettuce dosent do so well in aquariums but i dont know myself to be perfectly honest

 

[Byron]

I didn't get into the floating plant species in my previous post as we need the other data to complete the picture, but noobgamers mentioned a couple so I may be able to expand a bit.
 
I've had floating plants in my tanks for more than 20 years, and always include them for their benefits.  Presently I have Frogbit (in 2 tanks), Water Lettuce (in four tanks including in one with Frogbit), Water Sprite (in three tanks), and Brazilian Pennywort left floating in one tank.  In the past I have also had Salvinia.  I have duckweed in one tank mixed in with Water Lettuce.
 
Duckweed has its uses, but generally in display tanks I would go with one of the more robust floating plants.  The leaf spread is more interesting, the dangling roots provide interest and a source of food for fish as well as protection for fry.  Any of the species mentioned will manage under decent light, and fertilization with a comprehensive liquid is usually beneficial.
 
Water Lettuce can get large; there is not a "dwarf" variety as one can read from some sources, but growth is governed by the light and nutrients and I have found it easy to keep on the small side.  It reproduces fairly rapidly, so in most of my tanks I chuck out a handful or more each week during the water change.  Most of this is on the small side, around 1 to 2 inches across, but I have had plants I left that grew to 5 inches.  In the outdoor garden pond a few years back it was 8-10 inches in diameter.
 
The true tropical form of Frogbit, commonly called Amazon Frogbit, is a much better species.  I have the temperate species and it does not do as well, presumably because of the consistent higher temperature.
 
Byron.

 

[juhason]

The first thing I must sort out is the matter of using watts as a guide to intensity.  Watts is simply the amount of energy (electricity) a particular bulb or tube uses to produce the light it emits.  It really has nothing to do with the intensity or brightness.  As a quick example, I use T8 lighting.  The 48-inch tubes over my three largest tanks used to use 40 watts, but today they are being made to use 32 watts, yet the light intensity is actually a bit better.  The watts per gallon guide had some merit back when all tubes were much the same, in the days of T12, but no longer.  Watts is only a guide to intensity when comparing identical bulbs/tubes; for example, a 13w 6500K GE CFL bulb will emit more light than a 10w 6500K GE CFL bulb.
 
This "brown algae" we need to identify.  If it easily comes off with your finger, it is likely diatoms.  If it does not easily come off but needs scraping, it is probably a form of brush algae.  Excess nutrients can cause either, but so can too few nutrients, or too much or too little light.  To sort this out, I need to know the lighting you have (be specific) and the plant species.  Also, are you adding any plant fertilizers?  How often are water changes, and what volume, and are you vacuuming into the substrate.  What is the fish load like?  And what is the GH of your source (presumably tap) water?  All these factor into the balance.
 
A final example...my 70g tank has the "brightest" light of all my tanks, with two 32w T8 tubes for roughly a watt per gallon.  It is covered with Water Lettuce and Frogbit, and thick with lower plants like chain swords and larger swords, and moss everywhere.  I have to limit the light to no more than seven hours daily, or algae increases.  It is all about the balance.
 
Byron.

Wow thank you for the very well explained answer. I'm still a bit of a newbie to planted tanks so bare with me. I actually have two 32watt T8 bulbs as well labeled as "daylight" from Home Depot. That may actually be too much light, since your 70 gallon has the same thing! 

 
 
As for fertilizing, I used to do very minimal fertilizing about once a week or so, but then I had the diatom outbreak (I have identified them as diatoms based off your description) I stopped dosing, thinking that was why, but they are still a problem. I was dosing it with Aqueon Plant Food and Envy. Then also I was using liquid carbon daily. 
 
As for bioload I have 3 blackstripe topminnows, 4 golden topminnows, three 0.5" banded sunfish, two 1.5" northern longear sunfish, 2 bluefin killies, and a single bluenose shiner (lone survivor of a temperature malfunction). All my fish are relatively young and small so the bioload is probably a bit low for now.
 
Plants are large bundles of various crypts, water sprite (potted) green cabomba, a large grass-like plant (I'm not sure on what species it is, it was a gift...sorta) that is not doing too well, and a small remaining bundle of pygmy chain sword which is dying as well.  
 
I try to change the water every week, but some weeks I am just too busy, which could definitely be a problem in upsetting the balance of my tank. I change about 10% weekly if I can, if I miss a week, I do 20%. I vacuum the surface of my substrate, but I don't go into it since the top layer is sand and I don't want to lose any of it. I don't know my GH or how to test it. 

ive found amazon frogbit does really well as long as you keep it still otherwise it just floats around the tank endlessly but i started with 3 pieces and now have a 60cm square section of the stuff
ive heard that water lettuce dosent do so well in aquariums but i dont know myself to be perfectly honest

 
 

I didn't get into the floating plant species in my previous post as we need the other data to complete the picture, but noobgamers mentioned a couple so I may be able to expand a bit.
 
I've had floating plants in my tanks for more than 20 years, and always include them for their benefits.  Presently I have Frogbit (in 2 tanks), Water Lettuce (in four tanks including in one with Frogbit), Water Sprite (in three tanks), and Brazilian Pennywort left floating in one tank.  In the past I have also had Salvinia.  I have duckweed in one tank mixed in with Water Lettuce.
 
Duckweed has its uses, but generally in display tanks I would go with one of the more robust floating plants.  The leaf spread is more interesting, the dangling roots provide interest and a source of food for fish as well as protection for fry.  Any of the species mentioned will manage under decent light, and fertilization with a comprehensive liquid is usually beneficial.
 
Water Lettuce can get large; there is not a "dwarf" variety as one can read from some sources, but growth is governed by the light and nutrients and I have found it easy to keep on the small side.  It reproduces fairly rapidly, so in most of my tanks I chuck out a handful or more each week during the water change.  Most of this is on the small side, around 1 to 2 inches across, but I have had plants I left that grew to 5 inches.  In the outdoor garden pond a few years back it was 8-10 inches in diameter.
 
The true tropical form of Frogbit, commonly called Amazon Frogbit, is a much better species.  I have the temperate species and it does not do as well, presumably because of the consistent higher temperature.
 
Byron.

Thank you for the good info on the floating plants!! I really would love the look of the roots growing into the water. I think I will try to get some water lettuce (and hopefully it works out) and amazon frogbit. 

 

[Byron]

Wow thank you for the very well explained answer. I'm still a bit of a newbie to planted tanks so bare with me. I actually have two 32watt T8 bulbs as well labeled as "daylight" from Home Depot. That may actually be too much light, since your 70 gallon has the same thing!
 

 
You're very welcome.  You light is excellent.  My 70g is a shallower tank than your 55g, though the 70g is wider front to back.  But a dual T8 light system is good lighting.  And I use the same tubes, though I mix them.  One is a 6500K Daylight, the other is 5000K.  Phillips and Sylvannia make these, whichever HD stocks [here they now have Phillips, previously Sylvannia].  This mix gives a tad more red (the warm light) and I have found it good for plants and fish colours.  The "K" is the Kelvin which is the colour temperature of light.  The lower the K number, the warmer, and the higher the K the cooler.  Sunlight at midday is around this mix.  These tubes are high in the red, blue and green which have been shown to promote good plant growth.
 
You can now control things with duration.  A timer (a few dollars) is a wise investment so the photoperiod is the same every day.  I would start out with eight hours, and this can be any time you like.  Just as long as the tank is in complete darkness for several hours (no room light).  My lights presently come on at 10 am (the 70g at 11 am) and go off at 6 pm.  When I worked they came on at 1 pm and went off at 9 pm so I could enjoy the aquaria during the evening.
 

As for fertilizing, I used to do very minimal fertilizing about once a week or so, but then I had the diatom outbreak (I have identified them as diatoms based off your description) I stopped dosing, thinking that was why, but they are still a problem. I was dosing it with Aqueon Plant Food and Envy. Then also I was using liquid carbon daily.
 

 
Diatoms are normal during the first 2 to 4 months of a new setup because it takes this time for the biological system to establish and become stable.  If the tank is established, diatoms can occur from too little light, high silicates (certain minerals), and maybe a couple other things.  If they are just in the back, I wouldn't worry.  You can remove them during the water change.  Once the light and nutrients are balanced for the plants, this should disappear.
 
Fertilizers are important, by which I mean the type.  Nutrients occur in the source water and fish foods, and sometimes this is all that is needed.  However, you have some plants that need good light and thus more nutrients (Cabomba particularly), and the pygmy chain sword is a heavy feeder too though light can be moderate.  I would suggest you change to a comprehensive fertilizer.  Seachem's Flourish Comprehensive Supplement for the Planted Aquarium is what I use, but another similar is Brightwell Aquatics' FlorinMulti.  You use very little, about half a teaspoon once a week in your tank.  I'll have to look up the Aqueon and Envy to see what they contain.  As for the liquid carbon, I would not recommend this, though I don't know the brand.  Excel and API are glutaraldehyde which is a very toxic disinfectant that kills Vallisneria and some plants at normal dosage, and if overdosed can kill plants, fish and bacteria.  I use natural CO2 which occurs from the breakdown of organics by bacteria in the substrate, and of course respiration of plants and fish.
 

As for bioload I have 3 blackstripe topminnows, 4 golden topminnows, three 0.5" banded sunfish, two 1.5" northern longear sunfish, 2 bluefin killies, and a single bluenose shiner (lone survivor of a temperature malfunction). All my fish are relatively young and small so the bioload is probably a bit low for now.
 

 
I asked about this because of the nutrients from fish food/waste.  I would still use a comprehensive liquid supplement.
 

Plants are large bundles of various crypts, water sprite (potted) green cabomba, a large grass-like plant (I'm not sure on what species it is, it was a gift...sorta) that is not doing too well, and a small remaining bundle of pygmy chain sword which is dying as well.
 

 
The "grass" might be a terrestrial plant.  The others are aquatic, and need good nutrition.  Your light is fine, the only possible issue might be the Cabomba in time.  I cannot keep this beyond a few months with my moderate lighting.
 

I try to change the water every week, but some weeks I am just too busy, which could definitely be a problem in upsetting the balance of my tank. I change about 10% weekly if I can, if I miss a week, I do 20%. I vacuum the surface of my substrate, but I don't go into it since the top layer is sand and I don't want to lose any of it. I don't know my GH or how to test it.

 
 
First, increase the volume of your water changes to 1/3 to 1/2 the tank, and make sure it is every week.  This is important for plants and even more for fish.  I found the best way is to find a time (it only takes an hour or so) every week when you would normally be doing nothing else, and make that the water change day/time.  I use Sunday mornings.
 
Substrate cleaning sounds fine; some of my tanks never get the substrate cleaned at all, others only across the top (all sand but one is fine gravel).
 
On the GH, check the website of your municipal water supplier, or if not there call them.  No point wasting money on a test you may only use the once.  The GH will not change in the aquarium, or very little, asnd we just want to know it.  Some essential plant nutrients come from the source water.
 
Hope this helps, don't hesitate to ask questions.  I'll attach a recent photo of my 70g for illustration as to what you can expect the way we are discussing; this is my flooded Amazon setup.
 
Byron.

 

[juhason]

 

Wow thank you for the very well explained answer. I'm still a bit of a newbie to planted tanks so bare with me. I actually have two 32watt T8 bulbs as well labeled as "daylight" from Home Depot. That may actually be too much light, since your 70 gallon has the same thing!
 

 
You're very welcome.  You light is excellent.  My 70g is a shallower tank than your 55g, though the 70g is wider front to back.  But a dual T8 light system is good lighting.  And I use the same tubes, though I mix them.  One is a 6500K Daylight, the other is 5000K.  Phillips and Sylvannia make these, whichever HD stocks [here they now have Phillips, previously Sylvannia].  This mix gives a tad more red (the warm light) and I have found it good for plants and fish colours.  The "K" is the Kelvin which is the colour temperature of light.  The lower the K number, the warmer, and the higher the K the cooler.  Sunlight at midday is around this mix.  These tubes are high in the red, blue and green which have been shown to promote good plant growth.
 
You can now control things with duration.  A timer (a few dollars) is a wise investment so the photoperiod is the same every day.  I would start out with eight hours, and this can be any time you like.  Just as long as the tank is in complete darkness for several hours (no room light).  My lights presently come on at 10 am (the 70g at 11 am) and go off at 6 pm.  When I worked they came on at 1 pm and went off at 9 pm so I could enjoy the aquaria during the evening.
 
As for fertilizing, I used to do very minimal fertilizing about once a week or so, but then I had the diatom outbreak (I have identified them as diatoms based off your description) I stopped dosing, thinking that was why, but they are still a problem. I was dosing it with Aqueon Plant Food and Envy. Then also I was using liquid carbon daily.
 

 
Diatoms are normal during the first 2 to 4 months of a new setup because it takes this time for the biological system to establish and become stable.  If the tank is established, diatoms can occur from too little light, high silicates (certain minerals), and maybe a couple other things.  If they are just in the back, I wouldn't worry.  You can remove them during the water change.  Once the light and nutrients are balanced for the plants, this should disappear.
 
Fertilizers are important, by which I mean the type.  Nutrients occur in the source water and fish foods, and sometimes this is all that is needed.  However, you have some plants that need good light and thus more nutrients (Cabomba particularly), and the pygmy chain sword is a heavy feeder too though light can be moderate.  I would suggest you change to a comprehensive fertilizer.  Seachem's Flourish Comprehensive Supplement for the Planted Aquarium is what I use, but another similar is Brightwell Aquatics' FlorinMulti.  You use very little, about half a teaspoon once a week in your tank.  I'll have to look up the Aqueon and Envy to see what they contain.  As for the liquid carbon, I would not recommend this, though I don't know the brand.  Excel and API are glutaraldehyde which is a very toxic disinfectant that kills Vallisneria and some plants at normal dosage, and if overdosed can kill plants, fish and bacteria.  I use natural CO2 which occurs from the breakdown of organics by bacteria in the substrate, and of course respiration of plants and fish.
 

As for bioload I have 3 blackstripe topminnows, 4 golden topminnows, three 0.5" banded sunfish, two 1.5" northern longear sunfish, 2 bluefin killies, and a single bluenose shiner (lone survivor of a temperature malfunction). All my fish are relatively young and small so the bioload is probably a bit low for now.
 

 
I asked about this because of the nutrients from fish food/waste.  I would still use a comprehensive liquid supplement.
 

Plants are large bundles of various crypts, water sprite (potted) green cabomba, a large grass-like plant (I'm not sure on what species it is, it was a gift...sorta) that is not doing too well, and a small remaining bundle of pygmy chain sword which is dying as well.
 

 
The "grass" might be a terrestrial plant.  The others are aquatic, and need good nutrition.  Your light is fine, the only possible issue might be the Cabomba in time.  I cannot keep this beyond a few months with my moderate lighting.
 

I try to change the water every week, but some weeks I am just too busy, which could definitely be a problem in upsetting the balance of my tank. I change about 10% weekly if I can, if I miss a week, I do 20%. I vacuum the surface of my substrate, but I don't go into it since the top layer is sand and I don't want to lose any of it. I don't know my GH or how to test it.

 
 
First, increase the volume of your water changes to 1/3 to 1/2 the tank, and make sure it is every week.  This is important for plants and even more for fish.  I found the best way is to find a time (it only takes an hour or so) every week when you would normally be doing nothing else, and make that the water change day/time.  I use Sunday mornings.
 
Substrate cleaning sounds fine; some of my tanks never get the substrate cleaned at all, others only across the top (all sand but one is fine gravel).
 
On the GH, check the website of your municipal water supplier, or if not there call them.  No point wasting money on a test you may only use the once.  The GH will not change in the aquarium, or very little, asnd we just want to know it.  Some essential plant nutrients come from the source water.
 
Hope this helps, don't hesitate to ask questions.  I'll attach a recent photo of my 70g for illustration as to what you can expect the way we are discussing; this is my flooded Amazon setup.
 
Byron.
 


Thank you so much, you're a huge help! You're tank is beautiful, I hope to have a tank like yours. I love the look of the roots at the top, always have. I tried looking online for the GH but couldn't find it so I may have to call them and get back to you about that. As for the grass plant, I think it is an aquatic plant, it looks like a plant I have seen in numerous tanks, just don't know what it is called. It looks kind of like pygmy chain  sword expect that it is not pygmy whatsoever. And thanks for the mixing light bulbs tip. I do love the warmer look it gives! And I have actually really been trying to get a timer these past few weeks, I just haven't had a chance.