# Using plants to lower nitrates



## Fishman123

Hello everyone. In your estimation, how well can plants reduce nitrates? I'm asking because I'm thinking about setting up a large tank with big fish and making something like a freshwater refugium to keep the water clean. I'm thinking I would be able to set up something like a sump, and have the main section house an easy, fast growing plant like java moss or something. Do you think it would be worth it? Or do plants only take in so little nitrates it would be a waste of time? Thanks for any opinions.


----------



## hoppycalif

Plants will take in a negligible amount of nitrates unless you also supply adequate phosphates, potassium, trace elements and a source of carbon. And, of course, you need adequate light to drive them to grow fast enough to use the nitrates. A short cut is to use emersed or floating plants, which get their carbon from the CO2 in the air. But, those still need the other nutrients.


----------



## Robert Hudson

Its really dependent on light and C02 more than anything else. The faster the growth rate, faster metabolic rate, the more nitrogen plants will up take. Higher levels of light and C02 is what increases the growth rate.

In moderate to high light levels, you need to keep nitrate levels at 15 to 20ppm just to feed the plants. Then you will be adding nitrate to your water, not worrying about trying to lower it. Most hobbyists who have a heavily planted, well balanced aquarium constantly have un measurable levels of nitrate.

Now if you do not want a heavily planted high tech tank, and are just looking at using plants as a biological filter, then consider setting up a planted sump, refugium as a filter. Then you can use house plants and other terrestrials to suck up nitrate.


----------



## KatjaT

Good houseplants to use to lower nitrate: _Epipremnum pinnatum_ and _Ficus pumila_


----------



## TWood

The only reason I started keeping plants was to control nitrates, thinking I could lower my maintenance chore. Imagine my dismay to discover that keeping plants is more of a PITA than the fish. As others have mentioned, if you provide all the other required inputs it is fairly easy to drive nitrates to zero. Then the plants stall and you have to actually add more nitrate. If all you want to do is control nitrates, and if you don't mind changing water, and your tapwater is reasonable for the fish, it's way easier to just do water changes.


----------



## Oreo

Now that's not what I wanted to hear at all. Granted, I hate doing water changes on my 30gal, so doing them on my new 110gal will be SUPER PITA. But I was really hoping that by going with a planted tank I'd have less maintenance once I got it all set up & running propperly.

Is it really that bad?


----------



## hoppycalif

If you look at having a planted tank as being a hobby, and a hobby is something you enjoy working on, then it isn't bad at all that a planted tank requires a lot of work. And, it does, generally. However, if you follow the "el natural" method, per the forum devoted to it here, you will have a lot less work once you get the tank set up and running well.


----------



## TWood

hoppycalif said:


> However, if you follow the "el natural" method, per the forum devoted to it here, you will have a lot less work once you get the tank set up and running well.


Yeah, but the original poster said s/he wanted to keep large fish. That's inconsistent with a Walstad tank. (I refuse to call it 'el natural', because nothing about a tank is natural.) Those tanks rely on low inputs across the board to be low maintenance, which means low fish load too.


----------



## hoppycalif

TWood said:


> Yeah, but the original poster said s/he wanted to keep large fish. That's inconsistent with a Walstad tank. (I refuse to call it 'el natural', because nothing about a tank is natural.) Those tanks rely on low inputs across the board to be low maintenance, which means low fish load too.


That just shows my ignorance about "el natural" tanks. I have never had one, so I haven't spent much time reading about them. What you say makes sense though - big fish equal big poop equal needed water changes, and that is contrary to the el natural "rules".


----------



## Diana K

I have used a planted sump in conjunction with a planted tank when I had a larger fish load. They can work well. Emersed plants is definitely the way to go. Golden Pothos, and Heartleaf Philodendron, are pretty good, other house plants can look REALLY great when they are being fertilized by fish water. I had an odd prayer plant that took off and grew leaves almost 6" across in such a sump. 

A sump that is up to 10% of the volume of the tank will help, but not totally remove nitrates. I would add potassium fertilizer to this sort of set up, but let the other ferts go until you notice some deficiencies. Emersed House plants will show deficiencies more consistent with land plants, not aquatic plants. 

A sump that is larger than 10% of the tank volume, and relatively long and low can grow enough plants, marginal pond plants, or house plants to remove all the nitrogen produced by some big, productive fish. 
I would set up such a system similar to a hydroponic garden, with 1/4" or so diameter lava rock as support media. Plenty of water movement, room for beneficial bacteria to grow, good support for the plants. It might be so showy that you would have it on display right next to the tank.


----------

