Nitrate levels

  1. Dempsey Dude Well Known Member Member

    Hi all,

    So my 20 gallon tank has been running for over a year now, and I have slowly gotten it to the point where it is quite heavily planted (tons of growth, green all over). Actually at this point I have (I am embarassed to say) not done a water change in this tank in about a month, due to being extremely busy with a new job and taking an online course. I checked the nitrates today and the levels are lower than I've ever seen them, almost negligible. I also overfilter this tank, I am running an Aquaclear 30 and an Aquaclear mini, where the mini itself could probably handle the filtration on its own. Is it possible that the amount of plants combined with the filtration has gotten it to the point where water changes would be almost unnecessary in this tank?
     
  2. atc84 Well Known Member Member

    very good question. technically, yes.

    The reason why your nitrates are so low is because the nitrogen components that make up these toxins are being used by the plants faster than the fish can poop. I actually over feed my fish because without nitrogen, the plants will not grow very well. It's like fertilizer for terrestrial plants. The filter doesn't necessarily make a difference either. The filter is just grabbing all the fish waste before it can reach the substrate, where the plants are able to use it. By having a lot of mechanical filtration, you are actually dumping out all the the fertilizer for the plants. This is why in my 29 gallon tank i just have a powerhead that cycles the water, and the plants along with the lava rock decoration that has a very porous material for the bacteria to grab on to keep the water clean.

    I havn't done a water change in a while either. I stopped keeping track, it's probably been a month, and my water looks great. Nitrates at 0-5, plants are growing fine, fish are happy. The only reason why i change the water is because:

    algae: generally over time an excess of nutrients will cloud on the surface of the sand in my tank, which is a good reason for some algae growth. Since the last water change i havn't noticed any algae, which must mean my tank is still in a good balance.

    TDS: Total Dissolved Minerals is a phenomenon discussed by aquarists as an effect of replacing evaporated water with tap water, which means you are replacing water without minerals with water with minerals. The increase of minerals causes the TDS to rise, which apparently is bad for the fish. This isn't proven, it's just something to think about.

    macro-nutrients: i might've mixed this up with micro nutrients, but basically the plants will use up trace elements that are needed for good growth. Things like potassium, iron, calcium, you get the idea. Without these nutrients algae can break out again. Tap water contains these elements, along with seachem flourish, so i guess if you dosed the aquarium then this doesn't matter.

    appearance: I generally do a water change after i stick my hands in the tank because the water gets really dirty. Also, in a tank with wood, tannins will become apparent over a long period without a water change.

    These are the secrets that make up low-tech "self-sustaining" tanks, that is based on the walstad method.

    So why can't i throw in tons of fish into my tank since the plants clean the water so well? This is a question that is debated a lot, and the limiting factor is essentially how crowded you think the tank is. You could stock a tank with top dwellers such as guppies, moderate dwellers such as tetras, and then cories on the bottom. This would work great, and it would look like a very full tank, and everybody is happy.

    Sorry for the book, i really liked your question. :)
     

  3. Thai Aquarium owner Well Known Member Member

    Although I have heard frequently that larger tanks can be run without filters, due to all the planting and the substrate actually processing the water, yours is the first I have heard of being a fairly small tank.
    +1 on atc statement that the filter will have very little bearing upon the readings.
    You seem to have the balance really good between plants, substrate , fish Etc in the tank
    Good luck with the tank, and I hope it remains W/C free
     
  4. Dempsey Dude Well Known Member Member

    Thanks for the in-depth and illuminating responses! I switched my smaller filter on this tank to low-flow so that I wouldn't run the risk of over-filtering and starving the plants. I will continue to do water changes but more sparsely because I do want there to be a balance in the nutrients present and I do not want the TDS syndrome you mentioned. As for algae, I never really see much of that, but I think that is because of my 2 SAE's, which I am thinking about moving to my 50 gallon soon anyway.
     

  5. Dark Sky Member Member

    I've been noticing interesting Nitrate levels recently too. I have two 29G's, I've just recently set the second one up. Originally, all my fish were together in a moderately planted tank. I moved the Goldfish out to their own tank, along with the plants, leaving the smaller fish (Neons, Danios etc) with a sand base and no plants (to start with). The nitrates in the goldfish tank have stayed around 5-10, while the other tank skyrocketed to a deep red within a few days. The conclusion I drew was the same as yours, the lucky plants were feasting on goldfish poop, while the 'clean looking' tank was turning into a sewer...