# effects of low light



## Minipol (Jul 4, 2006)

Hi,

i posted a thread in here on HQl lights. The reason why i asked about that is that i'm concerned that once i go for a NPT setup, the current lights won't cut it.
I have 4 x Philips TL'D 84 ( lumens: 3450, °K: 4000). That's rather low light for a 500l (+-125gal) tank. It's also deep @ 70cm (27.5")
I would like to run the tank without my current C02 & only 1 of the 2 filters left. Ideally no filters at all (except powerheads for watermovement).

Now i fear that if my lighting isn't allowing fast plant growth, they won't remove enough nutrients to cut both filters and that is my goal for this NPT.
Also, it's rather densly stocked, about 1cm per liter or about 1 inch per 1/2 gallon (if i'm calculating correct )

If this is the case then maybe i should look into setting up something else in this aquarium altogether. I still have another aquarium that might be more suited for a NPT.

What are your thoughts on this?


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## sb483 (May 29, 2006)

One trick is duckweed. The lighting is low at the bottom of the tank, but it's still pretty bright at the surface. If you have slow growing plants in the tank itself (java fern, java moss, anubius, ...), these plants will survive in a low-light regime. But they won't grow fast enough to take care of algae, or excess nutrients. However, duckweed at the top won't know about the low-light regime, so will probably show fast growth and eat up nutrients that would otherwise cause problems.


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## Minipol (Jul 4, 2006)

Indeed good remark. But as you said, i don't think they will be able to keep up with the nutrients. And what i really like about a heavily planted aquarium is the variety in plants.
If only a couple of plants species are in there, it's not as beautiful i think.

The more i think about it, the more i fear that my tank isn't suited for NPT unless i would go for T5 or HQl

Edit: I checked some pics i took from when i first setup the tank. I have gone through several setups and the first one included many plants and they all grew well apparently before algae took over so this could be an indication that the light is adequate even with the depth i have now to grow different species plants. Algae could have been because of the fact that i added fertilizer and didn't have a soil that provided the plants with an advantage.
This would mean i could give it a try anyway


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## sb483 (May 29, 2006)

Minipol said:


> Indeed good remark. But as you said, i don't think they will be able to keep up with the nutrients.
> The more i think about it, the more i fear that my tank isn't suited for NPT unless i would go for T5 or HQl


If duckweed can't keep up with the nutrients, then how can any variety of submerged plants? Submerged plants grow much, much slower than emerged/floating plants (from the Ecology book, due to lack of carbon) even with the brightest light.

Whatever lighting you choose, I hope it works out well. But since all submerged plants are shade plants (a graph in the book shows photosynthesis of submerged plants "maxing out" at a pretty low intensity), the extra lighting may just give algae more iron without helping plant growth. Hopefully the various plants you choose will absorb most of the nutrients, but if algae ever becomes a problem, remember the duckweed (and water lettuce, which kills algae in record time).


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## Minipol (Jul 4, 2006)

That's indeed a good remark but i'm not sure you can rely solely on the use of floating plants to keep the water clean. I might be the case however.
But i think that having submerged plants that are fast growers contribute a lot too.

Edit: 1 more thing. If floating plants are really that good, it would be possible to fight algae very effectively without to much plants in the tank itself. Diana recommends using lot's of different plants to see which do well and which don't so i guess it's better to use the 2.

If i would know it would be possible to rely heavily on floating plants, i would even try a different setup than what i had envisioned first. The tank i'm going to try Diana's recommendations on is setup as a South American one. Normally these are setup with not to many plants anyway.

That's why i'm having problems believing you can rely so heavily on floaters: if i would add only 3 big swords and some smaller ones and maybe a batch of egeria and then 2 or 3 types of floaters, (maybe even a lily) i can't see that taking care of all the waste the fish produce.

Don't get me wrong, if it would be possible, that would be very cool as you then could cut the filters, have a more sparsely planted tank, dimmed light by the many floaters and still combat algae effectively. It would IMO even be the ideal way of setting up a south american.

I hope Diana reads this and has some ideas if this kind of floater heavy based setups work as i think my angels would prefer it over a densly planted aquarium


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## sb483 (May 29, 2006)

I didn't say to use only floating plants, no submerged plants (besides, submerged plants are what make the tank look nice). If the tank does well with submerged plants only, leave it alone. But since algae shows up so often, a safer bet would be to throw in at least 1 variety of emergent aquatic plant (unlike nearly all submerged plants, duckweed doesn't really add much to the beauty of the tank; it's for algal protection alone).

Besides, in the book she says submerged plants are necessary to oxygenate the water for the fish.

*edit*: in ponds, floaters can look nice (sometimes). In tanks, it's the submerged plants that add beauty. I'm not advocating floater-heavy setups; a single floating plant will cover the tank if there are nutrients in the water for it to grow.


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## dwalstad (Apr 14, 2006)

Minipol,

I think sb483 has given you good advice. Thank you sb483!  

Since this is your first attempt and you seem unsure, I would start with a smaller tank than a 125 gal.

I have always recommended starting out with a large variety of submerged and floating plants. Basically, throw in the kitchen sink!

Diana


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## Minipol (Jul 4, 2006)

Diana, sb483,


i already started with something smaller. My first NPT is already purring away 

The thing that confuses me is that the book says to have about 2-3 watts per gallon yet when we talk about submerged plants, they are said to be all "shade plants" and that they "can't keep up with the growth of floating plants". I can see why and have experienced this in my tanks (duckweed)

Howevern, I fail to see the link between the 2-3 wpg and the fact the submerged plants are shad plants. Why would you want that wpg if the plants aren't using it anyway?

Or is it so that if you go with lots of floaters, light is less important and the 2-3 watts per gallon rule isn't as important any more?

Besides if floaters grow so fast and have aerial advantage, why would you need other plants?
Couldn't you just get by with say, duckweed & water lettuce?
That's why i'm confused. It would really be a nice experiment i think.
For instance, i can calculate my surface and say, let 75% of that surface be taken over by floaters and then it would be nice to know what fishload (ammonia production) they can filter.

I like floaters better actually as you can see more of your fish (less submerged plants) and a lot of fish tend to behave more naturally in less bright light.

As for my tanks, i have 3: a 500l & a 300l that i would like to convert & a 60 l that is already converted.
I will probably only convert the 300l of the 2 bigger ones.
I'll convert the 500 l to a MidAmerican or Malawi setup.
Probably mid american.


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## sb483 (May 29, 2006)

A pond with _only _floaters has a substrate that deteriorates over time, and too heavy a cover of floating plants prevents oxygen from entering the water. That's why pond owners need submerged plants like elodea - its roots prevent substrate deterioration and its leaves release oxygen that fish need to breathe.

In tanks, the same holds true, plus submerged plants look good (don't they? it's subjective of course, but the leaves of a healthy submerged plant looks so beautiful. if you disagree take a look at one of Takashi Amano's books and you'll change your mind ).

Duckweed doesn't look so good - even a novice would recognize it as a weed - but tanks with duckweed have less problems with algae than tanks without. This is all I'm trying to say *Minipol*: it sounds like you're expecting higher light-levels to lead to luxuriant plant growth. It may, but it may also lead to algae. You might be disappointed if the variety of plants you choose doesn't prevent algae from taking over - just a sprinkle of duckweed over the tank is pretty good insurance against this.

(Finally, if you have a massive algal problem and you're just about ready to tear down a tank, try water lettuce instead. From the book, it releases the strongest alleochemicals and also has a rapid growth rate)


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## dwalstad (Apr 14, 2006)

If you want to grow only floaters, I would just use a very thing gravel or sand layer at the bottom. This will give provide surface area for aerobic bacteria without getting anaerobic substrate.

As for the oxygen, I'd just watch the fish. You can always add an airstone or more water circulation if you have to. Since floating plants use air CO2, the CO2 removal (via degassing) shouldn't affect them.

We can discuss wpg all day, but the proof will be in the pudding. It's your tank. Good luck!


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## Minipol (Jul 4, 2006)

Thanks for your comments sb & diana

@sb483
I do love the look of aquatic plants but i also love variation. With the depth of my tank, some plants seemed to not take at all. I tried a massive plant growth already and some seemed to die off. Off course the ones i liked 

That's why i searched for a way to alleviate this. I ended up here and after reading Diana's book i'm convinced it's possible only not convinced it can be done with my tank because of the height.

That's why i also decreased height by putting a very big layer of sand in 
I have always had duckweed in my tanks. Now they have disappeared. This has happened after my giant vals started growing fast. And it happened in both my 500l & 300l. 500l has vallisneria gigantae & other tank has smaller type of vals. I think i read something in the book that suggests that giant vals can have a significant effect on duckweed.

Anyway, even with duckweed, 2 eheim cannister filters and not to much light i had algae. Only brush algae. And after a stupid mistake on my part involving adding chemicals (never again) i had bluegreen algae.
The blue green algae has gone but the brush algae is still there. I hate it 
Nothing so annoyin that seeing all the lower leaves being taken over by brush algae 

As for floaters, on my plants list for this tank (if i would do a plant setup) there were at least about 15 different submerged plants and 3 floaters: duckweed, water lettuce and salvinia

And you're right that i expect better plant growth with more light or at least a better chance to grow red plants. I like a splash of red in there 
I mean there is a minimum of light that a plant requires to even grow so if you increase the light and nutrients & C02 are available, then it would grow faster 
right?

@diana
Well, the proof might be in the pudding but i'm a libra, an ethernal doubter 
Really if my tank was 50 cm in height, it would have been converted already.
If i would have more time, i would certainly try it. But it's already my 6th attempt to get the tank arranged so i like it and brush algae don't tick me off.
So i want to be well prepared before i embark on yet another aquascaping adventure (ok ok i admit i like aquascaping too )

One of the reasons i want to try (well did with the 60l one) to go for a walstadificiation (cool word eh ) of my tank is reduced maintenance.
Saves time. Time one can spend watching the fish.

In conclusion i want to save time and have a nice variety of plants. If i can't achieve both, it's a waisted effort for me (on that tank, i plant to convert my 300l). Then i better choose a biotope that doesn't have many plants


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