[Steve Pituch]

Per D. Walstad NH3 (ammonia) is toxic to plants. It doesn't have a charge and tends to permeate cell walls unrestricted. NH4+ (ammonium), which is normally a terrestrial plant fertilizer, is not. I think the problem is that they both exist simultaneously and their respective amounts vary with pH. A pH change can convert NH4+ to NH3 and kill fish and plants. Plants do prefer NH4+ over NO3.

I keep those Ehiem pebbles and ceramic cylinders in my filters for biological filtration, as I feel it can't hurt. I think it is dangerous to try to make NH4+ available to plants... too risky. Also adding NH4+ to a tank is taboo.

Steve Pituch

 

[Steve Pituch]

Everything is biomedia. Your crushed dolomite would act as biomedia. A biofilm forms on everything in the filter.....and the tank.

If you need a little more mechanical filtration use some aquarium gravel in one of the baskets with maybe a little fluff at the bottom of the basket, but the gravel will also function as biomedia.

Steve Pituch

 

[Steve Pituch]

Yes, I agree. That's why I often use gravel as a media. Its got surface area and acts as a filter media.

I think of the filter media and all of its bacteria as an extra amount of biofiltration. When you clean a filter the shock to the bacteria has got to be severe, putting the bacterial activity out of commission for a while. The biofilms in the tank, substrate, and plants are plenty to keep things going in the tank as if nothing happened in the filter. That's why when its time for me to clean a filter I go all out, often bleaching all the components. If I turn a filter off for less than 24 hours I don't worry about it hurting the tank when I turn it back on. But if its been off more than a week, its time to tear it apart and do a thorough cleaning (by that time everything is anerobic or stinky).

Steve Pituch