elusive_fish Posted February 6, 2010 Report Share Posted February 6, 2010 Hi all, Ive been reading on the forums here and elsewhere about how to create a polystyrene background for a fish tank and im now more confused than ever. The biggest question is really around cement usage. Do you need to coat the cement in epoxy or something else? Will cement by itself break down in water when it is permanently submerged? If you do need to coat the cement in epoxy resin and sand, then why bother cementing at all? If anyone is interested in my project, its not really a 'background' per se. I am going to get a aquarium around 220 cm x 60 x 60 cm made for my cafe and place seating bar style around 3 sides. The poly feature is a double sided wall that will run down the middle of the length of the tank. It has diagonal holes cut in it for fish to swim from one side to the other. Its basically to stop people watching the fish from starring at the people on the other side. The other benefit is that the fish will love swimming through the holes. If that doesnt make sense I will post a diagram. I want to make the background a deep grey/charcoal to really show off the demasonis/electric yellows etc that I will putting in there. If anyone in chch with experience feels like lending a hand or some experience there might be some breakfast and coffee in it for you Quote Link to comment Share on other sites More sharing options...
Carlos & Siran Posted February 6, 2010 Report Share Posted February 6, 2010 The cement will release lime and calcium into the water, the resin will seal it, the cement looks like stone, looks better than a lot of the plastic ones I've seen. Quote Link to comment Share on other sites More sharing options...
Ira Posted February 6, 2010 Report Share Posted February 6, 2010 Hmmm, you could probably make a concrete using epoxy as the cement. Be interesting to try, Something like 1-2 liters of epoxy mixed with heaps of fine sand...Then you wouldn't have any concerns over leaching. Quote Link to comment Share on other sites More sharing options...
reef13 Posted February 6, 2010 Report Share Posted February 6, 2010 i used cemix patch cement mix and i know others that have too it works very well, get some oxide powder, mix it with the cement and have a play around with it you will be able to get the exact colour you want that way. it works really well and the oxide powder comes in different colours. if you use the cement you will need to cover it in epoxy or yeah it will leech a bit, you don't need much and with a bit of sand takes off the shine and can look very very cool. good luck Quote Link to comment Share on other sites More sharing options...
elusive_fish Posted February 6, 2010 Author Report Share Posted February 6, 2010 The real challenge that I have is that my 'background' is huge, double sided and full of caves/holes. The idea of having to cement all of that several times, then epoxy is almost enough to put me off the project (not to mention that its going to get quite expensive). So the cemix patch by itself without epoxy is a bad idea? What about the cement stuff they use to seal water tight places? Quote Link to comment Share on other sites More sharing options...
reef13 Posted February 6, 2010 Report Share Posted February 6, 2010 I can't say about the sealing cement stuff as i have never used it but i think that with the cemix on a background that size it would take a long time before it stopped leaching into the water, the cementing was actually really easy in holes and things you just make it quite runny and sort of pour it over works really well but yeah i know it could get kind of expensive using cemix and resin Quote Link to comment Share on other sites More sharing options...
Caryl Posted February 6, 2010 Report Share Posted February 6, 2010 Si-sphinx posted a step by step method he used (and this will appear in the Aquarium World currently being printed). He found the concrete leached, raising the pH. Several weeks of major water changes did not bring it down enough so he coated it with several layers of resin in the end. One of our members used poly she cut with a hot wire her husband had made into a curved shape (and she heated it using a small blowtorch I think) then she siliconed gravel onto it. You could also silicone and sprinkle with sand. Quote Link to comment Share on other sites More sharing options...
spoon Posted February 6, 2010 Report Share Posted February 6, 2010 dont worry bout epoxy if its africans the oph increase with cemix patch is minimal any way you will still have to buffer the tank i just used cemix patch then acylic paint have used epoxy before on other backgrounds and i honestly dont think its worth the effort or the price i cabn also show you what the different effect is using different methods as i have a few different backgrounds here atm Quote Link to comment Share on other sites More sharing options...
elusive_fish Posted February 6, 2010 Author Report Share Posted February 6, 2010 Si has already been kind enough to email me his guide. Its well done and sounds like a solid technique. I'm still trying to figure out if I can cement or epoxy rather than both. Ive seen some awesome looking epoxy coated in sand backgrounds... but im not sure where I can find a suitable charcoal coloured sand. I'm very tempted to follow spoons suggestion of not epoxying over the cement as it will be rift lake cichlids. Im just scared that after a month I still have a thank with pH too high to put anything in. pH aside, does anyone know if the cement will still hold up well after a number of years submerged? As Im practically building the tank around the background it would be gutting if it started to wear/flake/crack exposing white poly after a while. Thanks all for your comments and suggestions Quote Link to comment Share on other sites More sharing options...
spoon Posted February 6, 2010 Report Share Posted February 6, 2010 well epoxy is certainly a very permanent way to go ,just an expensive way that may not be necessary i think there may be a difference between normal cement or concrete compared to cemix patch as i can honestly say ive had no problems with ph (ive had to buffer) and i have a considerable amount as my tanks 5ft and the background is very textured sand over epoxy is also very good also i have to say rock solid with the right epoxy. also as far as im aware you wont have a problem with cement as many garden ponds are made from it (and actually strucural rather than just sitting there) and they last many years my4age hasa cement coated poly background i know its been in at least a year perhaps he can say from experience Quote Link to comment Share on other sites More sharing options...
dreadbunny Posted February 7, 2010 Report Share Posted February 7, 2010 If your going to put in africans just concrete will be fine, and much cheaper too. I left my concrete backgrond in the bath for a week changing the water everyday just in case it leached any nasties. 1 year on the ph in that tank is around 8.5 and they are happy as. Quote Link to comment Share on other sites More sharing options...
elusive_fish Posted February 7, 2010 Author Report Share Posted February 7, 2010 If your going to put in africans just concrete will be fine, and much cheaper too. I left my concrete backgrond in the bath for a week changing the water everyday just in case it leached any nasties. 1 year on the ph in that tank is around 8.5 and they are happy as. was the pH at 8.5 after the week of soaking and stayed that way for the year? Any sign of the cement degrading at all? Quote Link to comment Share on other sites More sharing options...
dreadbunny Posted February 7, 2010 Report Share Posted February 7, 2010 The pH was probably closer to 9 soon after I put it in so nothing too extreme. the concrete has a few dings in it where I've hit it when putting rocks in the tank, but it hasn't ever flaked off or anything. Quote Link to comment Share on other sites More sharing options...
elusive_fish Posted February 13, 2010 Author Report Share Posted February 13, 2010 Just a quick question for those that have done a cement covered poly background. It may sounds like a slightly dumb question, so apologies in advance The cement looks considerably darker while its wet, but dries out much lighter. When it is wet again after curing it gets the dark look back again. But does it look this dark when it is submerged and in place? The reason I ask this is that my neighbour used the local beach sand as a substrate in his aquarium. The sand looks dark when in the wet areas on the beach, but much lighter when dry. We figured it was in water it would look like it did when wet on the beach. Nope - it looked consirably lighter than expected. Quote Link to comment Share on other sites More sharing options...
spoon Posted February 13, 2010 Report Share Posted February 13, 2010 concrete on its own wont go too dark a if you want i can show you samples of two different methods i have used that have been submerged for over a year and 4 months respectively one is cemix patch painted wit acrylic and the other is decent epoxy with river sand on it both are rock solid interestly enough sand over epoxy retains that wet look in being darker than what it is dry Quote Link to comment Share on other sites More sharing options...
elusive_fish Posted February 13, 2010 Author Report Share Posted February 13, 2010 I realise that cement itself is quite light when dry (and that I will have to add black oxide to darken), but im just trying to understand if it would look the same submerged in water as it does when I hose it down outside Quote Link to comment Share on other sites More sharing options...
spoon Posted February 13, 2010 Report Share Posted February 13, 2010 if its fully cured it should Quote Link to comment Share on other sites More sharing options...
WEKA Posted February 13, 2010 Report Share Posted February 13, 2010 I have a cemix patch over poly background which I have used black oxide to colour and have epoxyed the back. I am about to epoxy the front and coat with dark sand from Taylors Mistake. I have a hot wire cutter which you are welcome to borrow if you wish. I also have a quantity of black oxide you can have. Send me a PM if I can help. Quote Link to comment Share on other sites More sharing options...
Ice222 Posted October 12, 2010 Report Share Posted October 12, 2010 I have some similar questions regarding DIY poly background and cement as well, so I thought I'd post here to keep al lthe info together. I've looked up Cemix, but there are so many different types! What are people using, or would recommend? Cemix Premixed Cements Cemix Bituproof Plus I'm going for a dark, almost black background, preferably with a rocky/stone-like look and texture. I would most likely coat it with epoxy resin to be safe, unless if the Cemix Bitproof stuff would be good enough on it's own. Also does black oxide retain it's sandy look when used with cemix? If not would anyone know where I could source some fine grained black sand? Any help or info would be appreciated. Quote Link to comment Share on other sites More sharing options...
WEKA Posted October 12, 2010 Report Share Posted October 12, 2010 The product I used was called Cemix Patch. The black oxide is a very fine powder, no texture at all. I had trouble sourcing black sand so ended up using sand from Taylors Mistake beach which is quite dark. The epoxy resin coating made it look dark. Quote Link to comment Share on other sites More sharing options...
Ira Posted October 12, 2010 Report Share Posted October 12, 2010 I have some similar questions regarding DIY poly background and cement as well, so I thought I'd post here to keep al lthe info together. I've looked up Cemix, but there are so many different types! What are people using, or would recommend? Cemix Premixed Cements Cemix Bituproof Plus I'm going for a dark, almost black background, preferably with a rocky/stone-like look and texture. I would most likely coat it with epoxy resin to be safe, unless if the Cemix Bitproof stuff would be good enough on it's own. Also does black oxide retain it's sandy look when used with cemix? If not would anyone know where I could source some fine grained black sand? Any help or info would be appreciated. The Bituproof plus appears to be asphalt based. Not really something I'd likely want in my tank. Quote Link to comment Share on other sites More sharing options...
Ice222 Posted October 13, 2010 Report Share Posted October 13, 2010 The Bituproof plus appears to be asphalt based. Not really something I'd likely want in my tank. Is it? How do you tell? I just thought it sounded liek it might be safe, as it said 'non toxic' and 'no fumes' Quote Link to comment Share on other sites More sharing options...
David R Posted October 13, 2010 Report Share Posted October 13, 2010 I used Cemix Mortar with black oxide for mine. Still have about 975g of the 1kg pack of oxide left if anyones interested in it.... Quote Link to comment Share on other sites More sharing options...
Ice222 Posted October 13, 2010 Report Share Posted October 13, 2010 I used Cemix Mortar with black oxide for mine. Still have about 975g of the 1kg pack of oxide left if anyones interested in it.... I'll be keen. Finding something I can use is why I'm asking all these questions in the first place. I'll pm you. Quote Link to comment Share on other sites More sharing options...
Josh_S Posted October 13, 2010 Report Share Posted October 13, 2010 CEMIX BITUPROOF PLUS is a specifically formulated stable FLEXIBLE bituminous emulsion for sealing and waterproofing concrete and concrete block walls below and above ground I use a similar product at work (Im a waterproofer). I would definitely advise against using it in a fish tank. It is bitumen based, basically the same stuff on your tar-sealed road. Quote Link to comment Share on other sites More sharing options...
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