View Full Version : When do I know if I need ferts/CO2

03-09-2011, 11:51 PM
I'm really starting to like having a heavily planted aquarium, but I'm not sure if maybe I'm taking it too far? Is there some sort of practical limit (other than size), to how many plants you can grow?

Right now I have a
25 Gallon (tall)

2x Large Bunches of Hornwort (weighted down)
1x Small Bunch of Hornwort (weighted down)
1x Small Bunch of Anacharis (floating)
3x Small branches of Anacharis (planted)
2x baseball sized clumps of Java Moss
1x Medium Amazon Sword
1x Medium Ozelot Sword
1x Small Anubias
1x Large Sagittaria

Full Spectrum 15 watt flourescent (so I have low light)
Everything except the Java Moss and Anubias are planted for full light (not shaded at all).

I also were going to add a floating Water Sprite and a Java Fern, but I'm not sure if there will be any problems for nutrients?

I think the two sword plants need iron, right?

Also, should I remove the rooted plants from their pots? Right now the two sword plants are in pots, which I buried under the gravel. Should I remove them from the pots and plant them directly into the gravel, or are they alright in the (plastic) pots. There's plenty of holes in the pots for roots to get out.

Lady Hobbs
03-10-2011, 12:01 AM
You have only 15 watts on a 25 gallon? Low light is considered 1-2 watts per gallon. You are really low light plus have a tall tank so you might want to think of adding more lighting?

03-10-2011, 12:05 AM
Just re-checked...
The light is actually 20 watts.

The lid is only ranked for 20 watts, would I need a whole new lid?

03-10-2011, 12:28 AM
Just checked my 10 gallon (also heavily planted)

50 watts!
That's 5 watts a gallon!

That has in it
1x Java Fern
2x Amazon Swords
1x Hornwort
1x Hygrophila
1x Water Sprite
1x Banana Plant
1x Sagittaria
1x Some very long leafy plant, just called "Specularia at the store"

My 25 gallon's plants seem to be thriving though. My hornwort and anarcharis have heavy daily growth. My ocelot sword, which has been in the aquarium for 2 weeks, has 2 new leaves sprouting.

Lady Hobbs
03-10-2011, 12:32 AM
You might want to go with something with more wattage like the 24" here. It's on legs to sit on top the tank or can be used with a glass hood.


If the plants are doing fine with what you have, then let them be. Yes, the swords should be removed from their pots and the wool around the roots removed.

03-10-2011, 01:04 AM
Keep in mind that watts per gallon is a very general rule-of-thumb type measurement.

Different types of bulbs will throw off this rule (CFL, T5, HOT5, T8, MH; all of these produce very different amounts of light when using the same amount of watts)

Also since tank dimensions vary, so will the amount of light that reaches your plants. Having 20 watts over a 20 long, which is only 12" high, will most certainly be different than 25 watts over a 25 gallon, which is 20" high. There is a threshold present for a lot of plants too. Just because you put 25 watts over a 5 gallon tank doesn't mean you can grow the hard-to-keep bright red plants out there, since the amount of light being produced is still just not all that much.

There's really no fast rule of thumb that's going to give you dead on accurate measurements for exactly what your plant needs. But, If you get a decent amount of lighting in the correct spectrum, keeping generally how tall your tank is in mind, you should be able to grow most plants you would want.

Once you have a decent fixture and bulbs, fertilizing your tank properly and injecting co2 will always give you healthier-looking plants than adding a ton of extra wattage, so keep that in mind, too. There is such a thing as too much light, and even just having a lot of light will have you constantly fertilizing and replacing co2.

Soooo, all that being said, the fixture LH showed you (or any other similar ones out there) would probably do wonders in your tank and you probably wouldn't have to touch much of anything :lol:.

03-10-2011, 01:11 AM
I can't afford a new lid :(

I'll keep an eye on the plants. If anything seems to be doing badly, I'll move it to the 50 watt 10 gallon to heal and maybe borrow the Java Fern from the 10 gal.

03-10-2011, 02:52 AM
First thing to keep in mind, watts is not a measure of light output, it is the amount of energy used by a given bulb. If you purchased Compact Fluorescent bulbs for your 10gal hood, you have 50 watt equivalent bulbs, not 50watt bulbs. In reality, you are probably only using about 14watts total on that hood, not 50.

Also, you don't need to go buying a new hood for your other tank. I ran a 40w T12 bulb on a 75gal tank and I had not problem growing Amazon Sword, Hornwort, Moneywort, Anubias, and Java Fern. Your plants should do just fine under the light you have. Why people always want to throw more light at plants then they need is beyond me.