Gravel Vacs And Nitrogenous Waste

  1. bopsalot Well Known Member Member

    Hello all! I never used to test my water for nitrogen compounds after a water change. Usually I will before. I typically do 40-50% once weekly.

    Anyway, nitrates seemed to be rising too quickly in my lightly stocked 60 gallon and I decided to keep a closer eye on things. Overfeeding, maybe? I started testing before and then 4-6 hours after a water change.

    Typically, I will vacuum around the hardscape and fake plants during a weekly water change. Every 4 weeks, I'll do a "deep cleaning", which just means I'll remove the plastic plants, scrub algae off of surfaces, and move hardscape around to vacuum the entire gravel bed.

    I have noticed that after a gravel vac, and especially after a deep cleaning, when I test the water 4-6 hours later, there will be ammonia (trace up to 0.5ppm) and sometimes nitrite (trace to 0.25ppm). These spikes usually resolve after 24 hours. Furthermore, nitrate is not reduced as much as it should be. A 50% change will bring nitrate from 30ish to maybe 20-25. You can barely tell on the color chart, but I confirmed it with dilution tests. Nitrate in my tap is 5ppm, which only accounts for some of this.

    Conclusion: Either:
    1. Thorough gravel vacs release pockets of ammonia/nitrite/nitrate into the water column from rotting waste in the gravel bed.

    And/Or 2. Seachem Prime (which I use at 150% recommended dose) is not neutralizing all the chlorine, thus temporarily damaging the BB colonies after a water change.

    Either way, I'm going to start thoroughly vacuuming all the waste at every weekly water change (all deep cleanings). (FYI, not sure if this is relevant, but I run 2 huge HOB filters on this tank with 4 big pads. I typically rinse 2 pads at each water change in old tank water. They hardly accumulate anything. And there are 4 huge biowheels). The tank has been cycled for about 4-5 months. Anyone else ever notice nitrogenous spikes after a gravel vac or a water change? Sorry about writing a novel...
  2. smee82 Well Known Member Member

    Ive never noticed anything in my tanks but mine are all planted and have mts.

    But my guess is that its from moving ornaments not the gravel. Ive seen bog piles of crud under my driftwood

  3. bopsalot Well Known Member Member

    Thanks! Yeah, tons of sewage and food particles come up from under the ornaments. I'm going to move everthing around each week and vacuum the whole gravel. It doesn't really take too long to put it back together. And I don't want that stuff rotting in the tank. Especially if it's going to release ammonia, nitrites, and extra nitrate.

    The angelfish used to do a great job eating all their micropellets. Now that they're bigger, they tend to scatter them around with their fins. The things break up and scatter. It's really a food for juveniles, best used in a bare bottom tank. I hand feed them, scattering a pinch each on various hardscape, but lately it's getting messy and stuff gets left in the gravel. Builds up and decays. Hence the extra nitrates. Time to grow up and eat flakes, but they obviously prefer the super high quality micropellets. All the fish go nuts for them, actually. The angels won't even come to the surface for food. So spoiled...:p