Science Project With Plants

[llamalord305]

So I'm gonna do my Science project on:

How do concentrations of CO2 affect aquatic plants?

I'm gonna get three 10gals, and put plants in them. I would like to know what plant would be the fastest growing. (Noticeable and measurable around a month) Would I need full substrate, or could I just put them in pots? How would that work? The simpler the better.

As for the CO2, what are my options? Can I get a CO2 tank and split the output into three fish tanks? With different amounts for each aquarium?
I was thinking of the soda bottle thing, with one soda bottle for one, two for another and three for another. Would these all produce the same amount of CO2 if they had the same amount of yeast and sugar? (That is, would each bottle produce the same amount?)

Fertilizers, what would I need?
Light, what would I need?
Would I need to cycle the tanks? Cause plants use ammonia? But if they are competing with the bacteria.... I don't know.

Hope that wasn't too overwhelming. Anything helps.
I'm gonna talk with my uncle tomorrow, he has done a lot of planted tank work.

 

[Jallen]

If you have light over 2 watts per gallon the CO2 is essential or the plants will die. Anything under is optional and it will help the plants so I'd go with somewhere between 1 and 1.5 wpg.

The tanks don't need to be cycled but because they won't be stocked you will need a fertiliser WITH nitrates and phosphates.

Play sand is the best option as a substrate as it's cheap but pretty good for growing plants.
I'd go with 1 litre soda bottles rather than 2 litres (so just half the normal 2 litre CO2 mix per bottle) and use 1, 2, or 3 of them.

The CO2 will need diffusing into the water, if you just let it float up to the top it won't do anything. The easiest way to do this with DIY CO2 is to put it right next to or under (whatever will suck it in better) the filter intake so the impeller chops it up into smaller bubbles and it spends longer in the water.

As for what plant to use, the best option would be a stem plant such as cabomba which will keep growing in length and produce side stems. You could get the cabomba, cut it to about 6" (keep the head, not the tail) stick the base in the substrate and it will root and grow. If you don't cut it at all then you can just measure the length.

 

[llamalord305]

Wow! As for fertilizers, would one with nitrtates and phophates be hard to find?
Would I have problems with algae?

 

[baron von bubba]

Wow! As for fertilizers, would one with nitrtates and phophates be hard to find?
Would I have problems with algae?

TPN+ is an all in one with everything you'd need!

and no, phosphates and nitrates DONT cause algae!
too much lighting, fluctuating co2 levels and ammonia are some of the things that can cause algae

 

[aaronnorth]

the variables in this are HUGE. i am not sure how accurate you are wanting this experiment to be?

measuring the growth you need to take dry weight for the most accurate answer. simply taking a measurment of the length isnt ideal as it some may have extra leaves, larger leaves, side shoots etc.

get a plastic food tub and put some sand in, but again, this can be another variable... do you want a nutrient rich substrate?

each bottle wont produce the same amount of CO2. differing quantites of yeast, sugar & water will affect this, unless you get an accurate scale.

measuring the CO2 in the water is the hardest part. We use drop checkers which lag behind about 2hrs, and they give us aprroximate values, unless you can get your hands on a CO2 analyzer?
KH/ pH relationship charts dont work.

different nutrient levels will also affect growth. hobby test kits arent accurate enough to carry out this experiment.

personally, i would go with something easier.......

get 3 tanks, put some egeria densa in, then see how limiting different nutrients affect growth.
eg,

tank1

dose phosphate, potassium & trace

tank2
dose nitrate potassium trace

tank3
dose nitrate phosphate trace


so in each tank you are missing out a macro nutrient,
use RO water so it doesnt contain any nutrients.

buying dry powders would be best for this because you can add what levels you desire without the need for testing

some figures:

NO3 - 20ppm
PO4 - 2ppm
K - 20-30ppm

so just make sure you underdose (or dont dose at all) for each figure.
you may get algae due to the plant dieing, rotting and producing ammonia.

but remember, you will see the defficiency appear first.

stick to low lighting so you dont need to worry about CO2.

 

[llamalord305]

Woah. Well, its too late, I got everything. I'm not planning to really "check" the CO2, since each bottle will contain exactly the same amount of everything. I'm gonna replace the yeast and sugar every week. All ferts will be the same.
The plants will be practically the same size right now, I helped my uncle unpack them today. Thanks for the replies!