Cheers but I don't have a sump on any tank.
Most of my tanks were built before I even knew what a sump really was!
I'm Using sand and internal filters on one tank.
(Medium planted low tech) normal stock. (8 fish 110 litre) all catfish. Glass cats and 2 plecs, one is growing out here.
This doesn't even conform to the accepted convention, the sand layer is 1" or less but it has a flow rig in that may be affecting things? That or the few rocks? Only two are on the floor, one is on the rig (weighs it down) with good space below.
Not sure, all I know is it always reads low! It normally only gets frozen food.
I only clean this tank to remove the ridiculous amount of plec poo! If it's left, the readings are low 0-3ppm but you need a spade to get the muck out!
Sand and externals on one tank. (120litre)
(Quite heavy planted low tech) well stocked.(technically overstocked)
1" sand (1"-2" substrate over maybe 40% of the tank).
This gets a good food mix everyday.
Loads of wood, covers a decent area of the footprint.
Cory Catfish and tetra.
These both record low nitrate. 0-3ppm I still do water changes but even if I leave it there is no real increase unless I disturb things, but it quickly recovers, both should have higher levels (according to other systems I have, nitrate should be 10-30 week to week, the first tank is often immeasurable, tanks with no substrate need water changes at least every week or more, these are 45,60 no subs & 110litres thin subs)
These tanks, the 45&60 have only one fish each, the 110 is stocked, 16 tetra 5 Cory.
The third system has an experimental remote dsb on it.
It might not work but it's too early to say, fingers crossed!
The last time I set this tank up it had a deep substrate and low nitrate, it was really well stocked and wasn't really planted (it had few plants, plec proof anubias and two giant amazon swords)
stock was 11 clown loach, 18"&15" plec, 28 peppered Cory catfish.
It's too much to say what's happening with this tank!
Loads of rocks (250kg approx)
half substrate at depth. Mixed blend, sand/gravel. Problems, hence the experiment! (750litre) last time around this tank ran sweet.
The key is creating anaerobic/anoxic conditions in parts of the substrate. Areas with less flow, under wood or rocks seems to be beneficial but I can't confirm this as I have had other "things" going on, sand/gravel etc.
Basically smaller particle substrates need less depth to create correct conditions.
Confusing? A little bit! But the pattern is quite clear!
