Why Does Nobody Like External Filters?

[rictheredneck]

deep down in the rock, its not much but it is something. Live rock isnt like a sponge in a filter, a sponge in a filter does its best not to allow bypass, live rock allows bypass and oxygenated water is only able to go through the outer areas, the outer areas contains nitrifying bacteria and inner areas contain denitrifying bacteria.

I THINK that once water reaches the inner areas of the rock the oxygen of the water is gone since the nitrifying bacteria on the outer areas have used it all.

i see what your saying - by the time water has reached the innermost part of the rock the oxygen is used up? are there any articles on this because i have never heared or seen anything about it. i agree with the deep sand bed is away of reducing nitrates but apart from getting a little sidetracked i havent really seen much evidence that external biological filtration is bad and produces a high level of nitrate.

pehaps if somebody had a canister full of filter floss and left it for an age there is just cause for concern from shying away from an external filter. but a canister full of ceramics which is alot easier to clean out than removing all the detrius from in on around and behind live rockwork surely cant be bad or am i missing a point here?

 

[Musho3210]

ive been confused with that part with detritus in the tank

I also said i think the oxygen is used up, i dont have any facts nor heard it from anyone, it is just a hypothesis.

 

[rictheredneck]

detrius and poop will colllect all round rockwoed in places its hard to get to.

 

[robbhp]

spoke to a dude at cascade he said he had just sold his last one a few days ago, said he should get some in by next week. i give trev a call and he said TMC had no stock of them and because of the two huracains they have just had , it my be some time before he will get some , but he did say he will ook out for them for me. big thanks fot the heads up though

i have to say i run my fx5 on my tank and although i have a small fish loads and give them very little food i have close to 0 nitrate, but that is just my take on it.

 

[thefirethief]

I think maintenance and media selection is the key here. When I started my first freshwater planted tank I couldn't understand why, despite having a healthy and high density of plants, a low fishload, and zero nitrates the tank was completely covered in Algae. Water changes galore made no difference until i realised I hadn't paid much attention to the Canister Filter for a while. The decaying matter in that was pumping nitrates straight back into the tank for the algae (and plants) to consume. I've now removed all media from it and use it for water circulation only and I'm nearly at an algae free tank. Obviously canister filters will always have its place in some systems but I could do without mine in most my tanks now.

 

[fraservet]

Yes, the problem with external filters is as has been said they are very efficient at denitrifying, which produces nitrates.
The flow rate is too high to provide hypoxic areas for nitrate removing bacteria to work.

Live rock on the other hand has millions of tiny little tunnels deep inside the rock which gives some areas with very low flow rates - no matter how many powerheads are pointed at the rock.
This is where the nitrate removing bacteria get to work.

An external filter is very useful in a fish only tank due to the large amount of waste produced, but not in a reef tank.

You can run a filter with live rock rubble as an alternative, or just providing chemical and mechanical filtration - provided you clean it out regularly.

Have a look at commercial nitrate removing filters, look how low a flow rate they require.

 

[rictheredneck]

Yes, the problem with external filters is as has been said they are very efficient at denitrifying, which produces nitrates.
The flow rate is too high to provide hypoxic areas for nitrate removing bacteria to work.

Live rock on the other hand has millions of tiny little tunnels deep inside the rock which gives some areas with very low flow rates - no matter how many powerheads are pointed at the rock.
This is where the nitrate removing bacteria get to work.

An external filter is very useful in a fish only tank due to the large amount of waste produced, but not in a reef tank.

You can run a filter with live rock rubble as an alternative, or just providing chemical and mechanical filtration - provided you clean it out regularly.

Have a look at commercial nitrate removing filters, look how low a flow rate they require.

surely they will only produce nitrate if there is nitrite ? i presume they cant make loads of nitrate if they dont have amonia/nitrite...
i am not saying that they they offer places with no oxygen or trying to say its better than live rock just why do they have a bad rep?