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High Nitrates in Moderately heavy planted tank


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Hi Everyone,

Wanted to start by saying that I went through the forum to see if I can find anything related to my issue, but couldn’t exactly. 

Here is my issue:


I have what one would consider moderately planted, if not heavy, 30G. I have swords, water sprite, xmas moss, epiphytes of various kinds, Crinum, Rotala- Green and Red, hornwort. 
I have also some new plants which are undergoing snail quarantine and will be added this week. That’s a mix of water cabbage, crypt and 2 green plants I forgot ID of. 
My HOB has destroyed most my water lettuce and only duckweed remains. The airline dam I use barely holds. HOB will go away in few months. 


I am battling High Nitrates despite all this for months. Ph stays around 7, Ammonia and Nitrite always 0. Ammonia may touch the 0.25 sometimes. I do weekly water change. Nitrates stay close to 40-80ppm  


I made a mistake of adding 3 root tabs in one go and that drove my Nitrates through the roof. This has been a problem since. Its been more than a month and nothing has helped except water change and that is also temporarily. 
I also added Easy green liquid for moss once last week but no use. 
I also add CO2 booster 3 times a week and only 1ml. This is less than recommended. 


I was struggling with black beard, hair algae and green dust. Most of which are under control since I did a blackout, taped half of my LEDs. 


1. Clearly my plants are struggling. What am I doing wrong? 
2. What can automatically contain my Nitrate apart from water change? 
3. Why are they not absorbing Nitrates like they should? 
4. Do I need more floaters? 

Thank you  





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What percent water changes are you doing weekly?

Have you tested the water coming from your tap/ water source? Water from my tap has nitrite and nitrates maybe you're experiencing the same issue.

I'll also mention if you know most of your nitrates are coming from the easy green (say 50% or more), I wouldn't overly stress over 40ppm nitrates. It is definitely something you should look to resolve, but isn't necessarily as urgent as something like ammonia or nitrite.

Heres my take on some of your questions.

1. Your plants look fine I wouldn't say they are unhealthy at all.

2. Floating plants like duckweed, water hyacinth, water lettuce or pothos can help in reducing nitrates. If your filter is causing any floating plants trouble you can try to make a floating ring either with airline tubing or straws to contain the plants.

3. It's not that your plants aren't removing enough nitrates it might be that you're expecting them to eat more than they can. A lot of your plants are fairly slow growers (in my opinion)and they look fairly new. At least to me your crypts, crinum and sword look like they haven't been in longer than a year. If I'm wrong let me know, but until they get bigger you might not see substantial uptake.

You could try propagating your hornwort and water sprite to several more plants. By doing this each piece will be its own plant and could absorb from their own roots instead of just the one. Looking at your hornwort I see a lot of side shoots coming at as it reaches the top, I would cut all of them off and replant them along the back while not crowding them together. Im assuming thats 1 or 2 stems in the right corner. But imagine if it was just 1 plant, that the root base for the hornwort has to spend a lot of energy feeding each and every single side shoot. It would grow a lot faster if it only had to feed the 1 stem rather than 5.

Also you could even  float some of the hornwort so that it has the max available light which will drive its nutrient uptake

Edited by Koi
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@Koi Thank you for the detailed answer.
Yes my tank is around 6 months old. Oldest plant is a sword. Rest I have slowly added. 
Hornwort is pretty new. Propagation is a good idea but wanted it to settle first. It is less than a month old. 

My floater ring does not hold as I like. Got to get creative with it. 

I will try your other tips and hopefully that works. There was a time when my Nitrates would never go above 20ppm. Thought adding more plants should reduce it even more. Need to figure out fert and algae balance. 

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As for your ring I think this could help as there are usually items most people have laying around

This is airline tubing and you can connect it either with a T or an airline valve. You could also just superglue the tubing together as well. If you use a T find some way way to block the other hole so water doesn't go into the tubing. I'm cheap so i just point the airline tubing upwards so I can still use the pieces I need



If you REALLY want to be creative you can connect the tubing together with a section of disposable chopsticks or 3-4 toothpicks (or whatever number you need to fit them snuggly inside)

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@Koiyes. That’s what I have right now but not enough due to my HOBs power. I have to really really be on top of it to ensure it doesn’t float towards it. I even attach it to a suction cup. 
Cannot wait for my filter cartridges to be over so i can just add another sponge filter. 
i have already have one large running along with the HOB. 

@Seized Yes. But its fairly new. Still establishing.  Hopefully it does as it is already growing like crazy. 

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I agree with @Koion floating plants. I bought a corral for them that has plastic attachments w/suction cups to hold the airline tubing in place, but lots of creative people on here have made them with everyday items (I saw one made with a plastic storage container top and airline tubing). Good luck!

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I finally purchased silicon tubing in double the typical airline diameter pretty cheap online (3/8” vs 3/16” of airline).  Then straight connectors to match.  I make my floating hoops with that now.

They are rather obnoxiously large but sooooo much more effective at containing floating plants than skinny airline tubing.  I have tucked them around heater cords (floaters either inside or outside the ring), around airlines going to sponge filters (floaters outside the ring), or bigger ones around both the HOB filter uptake and outflow with floaters outside the ring.  I’ve also cut the hinge section from the suction cup floating feeder rings and attached that section of the feeder ring to the floating ring to keep it where I wanted it.  Superglue is my friend, lol!

I have floaters in most of my small tanks but I like a combo of air driven sponge and sponge filled HOB’s (thanks Cory, for the idea to fill my HOB’s with sponge).  

Floaters seem to like flow below the surface but not too much surface agitation.  Hence the rings around the filters causing the surface agitation.  I have scads of frogbit and red root floaters sucking up those nitrates for me, even on my bare bottom hospital/quarantine tanks.

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