Where are my nitrates gone?

I believe I'm at the end of my cycle but today I noticed something very puzzling...

My last water reading was from two days ago:
ammonia: 0
Nitrite: 8
Nitrate: 100

After that reading I did a 25% water change.

Today I am measuring my water again and here's the values:
ammonia: 0
Nitrite: 0.02
Nitrate: 1

Where's all the nitrate gone? It's a fishless cycle but I have a bunch of plants.
I also have an infestation of brown algae and I've read that they really like nitrate but I can't seem to believe that they would eat up all that nitrate in such a small amount of time... Especially since there has been 8ppm nitrate converted...

I double and triple checked by doing the test again with my drip test.
I also have some strips laying around that test NO2 and NO3 and used those and the result came back the same... No NO2 and no NO3 so I'm puzzled...

I'll be adding some ammonia today and see how it evolved in the next few days but I'm optimistic that the end of my cycle is near...

 

What other plants besides the algae do you have? That COULD explain more than you think.

 

With that many Nitrites (8), you still have a little time left to cycle. Like you said, I would keep testing for the next few days and see what happens.

 

What other plants besides the algae do you have? That COULD explain more than you think.

In this thread you can see a picture of my tank: My first serious tank | Freshwater Beginners 441865
I have the list of plants but am not at home so can't give them straight away...
Now that I see the picture, the plants have grown quite a bit since I posted that picture

With that many Nitrites (8), you still have a little time left to cycle. Like you said, I would keep testing for the next few days and see what happens.

Yes I understand. That's why I added around 4ppm ammonia after I did the reading this morning.
Will check the water again tomorrow to see how it progresses.
Only if both ammonia and nitrite are at 0, 24 hours after I added that ammonia, the cycle will be completed.

 

I spy large java ferns! Beautiful tank btw . It's a lot of nitrate to go missing but how many java ferns do you have in there? They are nitrate hogs! I've got a well established 20L with 3 small java ferns and one large in it, that has an almost undetectable amount of nitrate always, the most I see it at would probably be somewhere around 3ppm, and my tap water comes out at 10ppm. If I test a few hours after a 50% water change, poof! gone lol
Not holding the ferns soley responsible but deffinitely a contributor, the other plants will be feeding from it too! I see what looks like an amazon sword and some Alternanthera reineckiI ( I think?) not sure about the others as I'm on a rather old mobile phone with a damaged screen

 

What test kit do you use?

 

That's a lot for plants to absorb, but my planted community tank regularly tests nil.

 

Virtually all plants will ingest nitrates to some degree. As a general rule of thumb the faster a plant tends to grow the more nitrates it will absorb in the course of it's life cycle. Fast growing plants like water sprite, water lettuce and duckweed for example tend to soak them up quickly. One problem you're going to have with a fishless vs. fish in cycle is that the only ammonia introduced into the tank is usually artificially introduced by you in a spike vs. slowly over time so you're going to see peaks and then valleys.

Contrast this with a fish-in cycle where the livestock are constantly generating small amounts of waste which tends to lead to a more gradual and modest curve as the bacteria grow in. Think of it like a machine where the input into the processor slowly gets transformed over time. Big input equals spike that eventually gets soaked up by the plants, when input stops levels drop quickly. If you're wanting a more stable cycle with more even levels to observe you can achieve this by adding smaller amounts of whatever you're using as an ammonia source but do so more frequently. What's your ammonia add cycle?

As for the algae problem the main things that affect this are light cycles and intensity and CO2. Your plants as they grow will naturally compete with the algae. Plants and algae for the most part only photosynthesize during periods of light. Plants start up and ramp down the process quickly so dividing periods of lighting until your plants grow in a bit more can help plants outcompete algae for nutrients including nitrogen from nitrate and could help stabilize your nitrate levels a bit if you set it up right. I played with my settings for about 2 months before I got them right. Now I struggle to get enough algae to grow to keep my algae eaters happy.

 

Virtually all plants will ingest nitrates to some degree. As a general rule of thumb the faster a plant tends to grow the more nitrates it will absorb in the course of it's life cycle. Fast growing plants like water sprite, water lettuce and duckweed for example tend to soak them up quickly. One problem you're going to have with a fishless vs. fish in cycle is that the only ammonia introduced into the tank is usually artificially introduced by you in a spike vs. slowly over time so you're going to see peaks and then valleys.

Contrast this with a fish-in cycle where the livestock are constantly generating small amounts of waste which tends to lead to a more gradual and modest curve as the bacteria grow in. Think of it like a machine where the input into the processor slowly gets transformed over time. Big input equals spike that eventually gets soaked up by the plants, when input stops levels drop quickly. If you're wanting a more stable cycle with more even levels to observe you can achieve this by adding smaller amounts of whatever you're using as an ammonia source but do so more frequently. What's your ammonia add cycle?

As for the algae problem the main things that affect this are light cycles and intensity and CO2. Your plants as they grow will naturally compete with the algae. Plants and algae for the most part only photosynthesize during periods of light. Plants start up and ramp down the process quickly so dividing periods of lighting until your plants grow in a bit more can help plants outcompete algae for nutrients including nitrogen from nitrate and could help stabilize your nitrate levels a bit if you set it up right. I played with my settings for about 2 months before I got them right. Now I struggle to get enough algae to grow to keep my algae eaters happy.

What's your secret? I've never gotten a planted tank picture perfect, I've always got a little staghorn here from too much ferts, a little green spot there....some brown algae on the glass, some hair algae on the water pipes etc. If anyone wants advice on how to get rid of algae I'm the wrong guy to talk to.

 

Here's the list of the plants. I don't know the common names as they are not listed on the card
Hygrophila corymbosa *2
Alternanthera rosaefolia minI * 2
Echinodorus bleheri
Microsorum pteropus * 2
Anubias heterophylla

What test kit do you use?

The JBL test kit which is common here in Europe. It's a drop test kit similar to the API kit I guess...

What's your ammonia add cycle?

When ammonia drops to 0 I wait a day or 2 before adding around 10ml of my diluted solution. This equals to around 4-6 ppm of ammonia in the tank.

 

What's your secret? I've never gotten a planted tank picture perfect, I've always got a little staghorn here from too much ferts, a little green spot there....some brown algae on the glass, some hair algae on the water pipes etc.

Not gonna say at all that I've got a panacea solution or that I don't still have to work things out. Have experienced virtually every type of algae over time with my 3 tanks - Hair algae, BGA, but biggest one is just your normal run of the mill green algae on plants and sides of the tank. Glass will always need scraped no matter what you do or who is in the tank, think that's pretty much just life. I used to pull out décor and scrub as it would turn greenish after about 3-4 weeks. My best trick has been modifying lighting and introducing the right tank dwellers. For anyone with plants Otocinclus cats changed my life, hands down. They're fickle little beasts and sometimes clean off some types of plants but refuse to clear off others for a while, but eventually seem to get to it.

Understand that CO2 can help some but I've not taken the dive so can't really advise anything there, others may be more help. Literally every problem I've had with algae I've solved with lighting. I use Finnex Planted Plus, but they tend to be pricey. Other brands will probably work about as well, but may require a bit more work to program or manage light cycle and intensity.

If things get really bad I tend to go lights out for 48 hours, scoop, scrub and scrape and then modify settings to try to get back on track. Other trick that commonly helps is to elevate lighting higher above the tank. Since light has to penetrate the water, raising it up a bit can reduce intensity and prevent conditions algae thrive in. I've found it to be a healthy mix of science and art.