I was thinking of using it as a quaratine or hospital tank and or a plant/lily tank, but I have had a cracking idea. If it will fit, the basis for one of two upflow filters for the fish pond. The filters will be upflow veggie filters of the american skippy style. This thread really deals with only the filter that will be in the above cistern, the other tank I will have to make, a "box liner " inside a concrete flagstone shell.
The ONLY place I can put filters is 'in' the return stream, there is NO space anywhere else that I am allowed to use.

Here, in section, is the proposal.

The "floater trap" is basically a piece of rigid plastic around the outlet from the tank, set up as a boom, to keep the likes of azolla in the tank. It works, I have already used the idea else where.
Flowrate through this thing, hmmmmmm not sure about.
The tank will hopefully go where T3 is shown below

but I am not sure if it will impinge on the area occupied by T2, ignore T1, if it does then it will have to take the full stream flow which is 1633 UK gph. Now the stream will untimately be set up with two pumps which will work on an either or basis so that normally only one is ever running. The pump supplying 1633 UK gph, an aquamax 10000lph will run when I want a 'visual stream' running. When I dont want the visual stream effect an aquamax 5500lph, or smaller, will be used to keep media etc ticking over. There is no possible alternative to this method of operation as the pump/stream plumbing is under several tons of concrete which aint going anywhere. The smaller ticking over pump is to save running costs, I 'hear' about those.
Oh, as birds bathe in the stream there will be some form of bird safe grating over the 'plug hole'.
Re cleaning, it is likely that I will have to lift the media out to clean the bottom of the tank as the adjacent wall is 9" of soild concrete block which will be 'awkward' to drill for more than 1" pipe. Plus there will be no room for a valve and a valve CANNOT go outside the wall as it would be too exposed to my delicate feet and shins so the alternative is a recessed screw on pipe end. Whilst these are available, I think, I am not sure it will be practical. The 'seal' of the type I has tried in 2" washes out of place if there is a flow and I dont want to loose the full tank of water. I will however be thinking about this

If I do decide to fit purge drains how do I drill pipe holes through 9" thick solid concrete block wall?
I think I have seen 1", maybe 1.25", masonary bits in the likes of B&Q and I think either my 850W Bosch or my Dad's old big Black and Decker could handle these but that limits me to either 3/4" or 1" pipe which might be a bit small. Incidently there are drains for 2 tanks under consideration and for one the hole might have to be drilled off the square so it may be deeper than 9".
I dont think my pocket will stretch to hiring/buying a core drill and the power unit and I am dubious about being able to drill a ring of parallel holes 9", maybe more, deep and then removing a core. The latter was hard enough through 2" flagstone.
So any other suggestions or stick with 3/4" or 1"?

-------------fishmaduk----------david---------------------

good idea, that tank is best used for a holding tank/plant tank, the ridges in the bottom make for a bad filter.

one idea that occured to me tho, did you consider using it as an atuo feed, ie sink it at water level with the ball valev so the pond tops up atuo maticly when the level goes down?

well done sean.

-----------fishmaduk--------------david-----------------

Phil V