external cannister filtration

[lionheart]

how good are these at biological filtration
ive bought one which turns over 1550/LPH
however i read a artictle that said they are not very good as a biological filter because very little oxygen is present in the cannister which stops the benifical bacteria from surviving,the one i have purchased is a 3 basket system which enables you to have 3 different mediums the sponge is at the bottom and the top of the cannister and u place your medium in the 3 baskets between the 2 sponges,the one i bought is self priming,also on the return hose back to the tank u can fit a spraybar,my first thoughts are this should be fitted above the water level,however i am unsure if u can place it below the surface,which in my opinion would make it more quiet,as u would not get the water noise, and i'm not 2 sure if the surface of the water would circulate- or move as good this way as obviously u would get better water circulation with the water falling from the spray bar back into the tank,
currently i am using a fluval 3plus internal filter which turns 700/LPH
would by using the 2 filters together enable me to stock more fish,or is it a case that regardless of how many filters u have running it will not enable you to increase your stock levels,

 

[jsoong]

You would have good O2 in the canister if your tank itself is well aerated. You do that by having lots of surface water movement. You can place the spraybar under water, but aim it so that it create a strong surface ripple. <Having the spraybar above water would be best from aeration standpoint, but it can be loud.>

Overfiltering a tank *might* allow you to increas your stocking, but I think that an overstocked tank must also have increased water changes as well. <Note that most filter's recommendated tank size is overly optomistic. You are under-filtering if you follow their guides. I would not consider a tank to be overfiltered unless you have 10 to 15 x turnover per hour. So you might have an over-filtered tank if it is less than 150-200 l in size.>

 

[lionheart]

well i didnt think it was possible to over filtrate a tank,the tank is 133 litres in size,so if it is possible to over filtrate what are the downsides to this and what problems can arise

 

[gzeiger]

When he says "overfiltered" he just means installing far more filtration capacity than required, such that the tank behaves chemically as if it were a much larger body of water. There's no harm done by that except that excessive water movement at some point can be stressful to your fish if they are adapted to slow-moving or stagnant water.

 

[lionheart]

ok well ive attached spraybars to both return inlets on each filter both the internal filter and the external cannister filter and placed them in such a way that they point upwards inwardly towards surface and rear of the tank there is good surface movement but not extreme as for current within the water it dont seem to bad as only 1 tall plant which is situated directly underneath spray bar as slight movement the rest of my plants are very still,
any way thanks for the advice u have given much appreciated,