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Re: Tank Backgrounds (long reply follows)

> Date: Thu, 26 Aug 1999 17:16:38 -0400 (EDT)
> From: busko at stsci_edu (Ivo Busko)
> Subject: Re: Tank Backgrounds
> I've been toying with the idea of adding a background to my planted
> tank, using similar construction techniques as described by James Purchase.
> I really would like to avoid permanently gluing something to the back glass
> pane, and the plexiglass with suction cups sounds as a great idea. I couldn't
> figure out however how to handle the potential problems associated with the
> small gap that will result in between the background and the back pane. Water
> could get trapped and stagnant in there. It could be a breeding place for
> small snails, out of reach of the clown loaches. Fry and even larger fish
> could get trapped in there. Sounds to me as a maintenance hassle, or even
> as a potential disaster. Anyone in the list that has experience in addressing
> these problems would care to comment ?

	During the development of FakeRocks (see shameless plug below) I looked
	at some other types of background and made some prototypes.
	Long (but I hope informative) post follows! :)

	The first was a simple sheet of acrylic painted on one side with
	a waterproof varnish and covered in sand, sand being thrown onto 
	the varnish while wet. This looked OK (probably would look better
	once algae started to grow on it) but for me it was a little flat.

	So I started to mess about with polystyrene blocks. This I could 
	sculpt and make ledges and caves and looked good up until the point
	where I covered it in epoxy, the epoxy ate into it so much that it
	lost all the detail I'd carved into the foam. Fine if you just go
	with it but the result just didn't do it for me. The idea was to
	throw sand onto the wet epoxy and build up layers. This has the
	advantage that the weight of the sand alone will keep the thing
	on the tank bottom, but the disadvantage that the polystyrene has
	bearly enough structural stability to support the weight and can 
	easily snap under the load before you get it into the tank. Also,
	in order to get any kind of depth to the caves and ledges the foam
	needs to be about 3inches thick which takes up quite a percentage of
	the tank volume. 

	Then I hit it. I cast polyurathane resin forms from actual rock
	formations. These are very strong, totally natural looking, and very
	It required much more effort but I thought that I want something 
	that's primarily natural looking (I don't have bubbling divers in my
	tank but hey, my son does) and is going to last. If you want to see 
	the kind of thing then look at my site:

	A note about fixing and anaerobic conditions. I use rubber suction
	cups to fix these formations. I use silicon to fix the cups to the 
	top two corners of the formation, the substrate holds the bottom edge
	in place. This works fine.

	You can attempt to seal the background of your choice with silicon
	at the edges (and loose the suction cups) to avoid dead water but in
	practice the background can never fit that well against the edges if
	it's rigid because most tanks have braces at the top edges or across
	the center. Also you have to start with an empty dry tank to do this
	making retro-fitting a pain.
	I fit backgrounds in two pieces using suction cups and butt the middle
	joint a tightly as I can. I accept that water will get behind and use
	a powerhead which is used to supply a little extra current during 
	the day to pull water from behind the formation. The formation sits 
	in the substrate but doesn't rest on the bottom of the tank so I get
	flow under it. The powerhead inlet uses a short tube which goes through
	a hole drilled in the formation. I use the powerhead rather than the
	inlet from my filter as it's easier to maintain.

	I'm playing with the idea of using the top edge as a surface skimmer
	by putting a foam insert along the top edge of the formation and
	letting water behind the formation that way.
	The foam would get cleaned at water changes to remove leaves and gunk.
	The thing that's putting me off trying this is that when the flow stops
	at night organic matter trapped in the foam may start to turn sour and
	in the morning I'll flush this mix into the main body of water.

	Too much text ? Ah well, it's done now.