You may know that I've set up the second ugliset fish tank on the plant apart from 'the cylinder'? It's a six by four by two foot deep plastic stock tank for my red belly pacu - it's still not eaten the two angels, a syno cat, two plecs and two keyholes that it's lived with for about four years.
Two weeks ago, I decided from the water chemistry readings that the existing pond filter was not enough. So I cut some holes in a 30 by 12 by 20 inch plastic storage box and used that instead.
The indoor 'pond' is 1300l (or 350g in us gallons) and this beast is set up inside on a couple of granite blocks. Water from the tank is fed from a pond pump (500pgh) directly into the bottom of this and goes up through a layer of pond filter foam, two inches of gravel and then through thirty pounds or 15Kg of Alphagrog. I keep the tank heaters in there, also to avoid them being smashed by the pacu. Just a note - if the pump fails and the heaters are still going, they are below the tank water level when the pump back syphons.
My point is this: I'd fed ths pacu quite well for a few days, too well because it refused a hand full of koi pellets and I went off to work. On returning, the stock tank looked a mess with the about the same ammount of pellets drifting around. These were netted out and the water tested.
Amm 0, Ni 0, Na 50.......! Weird thing was pH 6.8 - my target. I would have expected lower.
Alfagrog is amazing. I had an old fluval 404 external and an fluval 3 internal on that tank in tandem because both were mature and came out of the pacu's old tank.
Just amazing, how well this filter works..