Advise me on the right resin please?

[Servillius]

Guys,

I want to try make a false sand bed with my liverock partially buried in some of it. My plan is to set the rock in place, then pour a fiberglass resin into the bottom of the tank and cover it in sand until it dries. What I don't know is what resin to use. I need something that pours so it sets firmly around the rock.

Can anyone tell me what to use... I need fairly exact instructions, give me a brand and a place that sells it if you can.

Thank you for the help.

[NanoReefWanabe]

to me this sounds like not such a good idea...as debris and such will collect under the resin eventually, but depending on the size of your tank a gallon of west systems epoxy resin should work fine for you...small tank a quart may get you by, depends how thick you want the resin and how big the tank is...

as for doing it it is pretty easy...once you figure out the volume required for your size tank to the depth you want....you can easily mix the resin using the dosing pumps, stir and pour, apply sand when done poring...you should have about an hour i believe before it starts to setup......

[teesquare]

One hing I would be concerned about - is there is a significant amount of post cure shrinkage with either polyesther or vinylesther based fireglassing resins. This would mean that you will have a gap develop around the edge of the resin pour.
You may overcome some of the issue by filling the resin with enough sand.

But....I am not sure that this is a good idea. I don't think you will get teh results long term that you are anticpating.
A more natural approach using fine oolitic sands or even a bare bottom will create less complication.

Just a thought....
T

[glazer]

Hmmm, I'm not sure I'd want to pour resin into a tank like that but I don't have any other suggestions to achieve what you're after.... it doesn't really matter what I think any way right?..lol
I would caution you though... I've worked with a lot of resins over the years, boat building, casting and such and not knowing as to what depth you want to go in the "resin bed" I would caution you as to, not too much at one time. It's an exothermic reaction that takes place.... it makes heat, a lot. I've caught containers on fire before with too much material mixed up in them. I would be very concerned about any significant pours creating enough heat to actually damage the tank in some way... like cracking the bottom or side panes of glass. Just a thought, or perhaps.. a word of caution.

Steve

[der_wille_zur_macht]

you should have about an hour i believe before it starts to setup......

The set time is determined by the hardener used - you can pretty much choose a set time if you know the temp you'll be working at, by choosing the appropriate hardener. Some hardeners blush, which would not be desirable in this situation, so the OP should look for a non-blushing hardener.

as debris and such will collect under the resin eventually,

If poured in place, there will be no way for anything to get under the resin.

One hing I would be concerned about - is there is a significant amount of post cure shrinkage with either polyesther or vinylesther based fireglassing resins.

Zero shrinkage, in effect. Nothing to worry about.


I would be very concerned about any significant pours creating enough heat to actually damage the tank in some way... like cracking the bottom or side panes of glass. Just a thought, or perhaps.. a word of caution.

Steve

IME this will only be a problem if the resin is left in a mixing pot too long - once it's poured, the surface area is so incredibly large that it's able to "cool" as it tries to heat up. Plus, the materials a typical fish tank are made from (glass and silicone) can withstand very high temperatures - much higher than it takes to melt a plastic mixing pot.

All that said, I'm still not sure this is the best approach for the desired effect. To get stability in the rocks, you're going to need a thick layer of resin - that will be expensive. An inch-thick layer on a 90g tank (for example) might take $200 of epoxy!

Luckily there are other ways to solve the problem of creating stable rock structures. For instance, drill the rocks and use epoxy putty to secure acrylic rods inside them, then glue the rods to a sheet of acrylic below the rock. This adds stability, is cheap and easy, and isn't nearly as permanent as casting an inch of epoxy around rocks in the bottom of the tank.

[NanoReefWanabe]

i am certain water could find its way under the resin even if it is poured in place...Water can find its way through laminated glass panes, it can definitely find its way under the epoxy too...where the water goes the poop goes...

as mentioned i dont think heat will be an issue with epoxy resin...polyester is a different story though...and at that glass takes a tremendous amount of heat...think of your dishwasher heating up that glasses with 120* water...that is a lot hotter then any hot batches of resin i have mixed..

[glazer]

Man, I'm not here to argue.... I was just giving some friendly words of caution. As far as shrinkage goes... there is A LOT of shrinking that takes place in polyester resins. Like I said, don't want to argue, just Google it.

Secondly, heat no matter what the resin, be it polyester or epoxies can definitely be an issue. Large quantities of it, be it a mixing bucket or a deep pour can generate tremendous amounts of heat. True, spread out over a large surface area this is not a problem and you need to know how to catalyze it based on what you are doing with it. Sorry if I missed it but I didn't see what size tank we are even talking about or how deep the resin needs to be to anchor all the rocks in place. That's why I said not very much at one time. I've seen plastic containers melt down, dixie cups ignite. I worked in a place that a couple of guys got careless and caught the building on fire. They mixed up a 5 gallon bucket and then the roach coach showed up and they decided it was time for a danish.... a little research on the resins we were using showed lab tests where they generated heat of over 600°

It's not a matter even of whether or not the glass can take the heat, not all glass is the same, as an example you don't use anything but tempered glass in a halide fixture. Anyway... enough heat can be generated to catch the mixture on fire. Again, not to argue, plenty of fodder in a Google search to show this to be the case.

All I'm saying is be careful.

Steve

[Servillius]

Thanks for the advice so far guys. After reading up on the suggestions and cautions here and speaking with some friends with some knowledge of resins, I get the feeling I may be better off making a "concrete" out of resin and sand and using that to fill and shape my sandbed.

I concede there is always a small risk of trapping stuff under anything I put in, but I have to believe this is fairly minimal.

I will be running a test on the "concrete" mix this week and I'm looking forward to seeing what the end result looks like. My concerns are that I use a resin that is not toxic to my fish and corals. Can anyone suggest a good brand and product for me to try with first?

[der_wille_zur_macht]

People put (solid) starboard in the bottoms of tanks all the time without worries of trapping debris. Epoxy resin will form to the shape of the tank and adhere to the glass, without shrinking, nothing will get under it. Any brand of marine quality epoxy resin will work fine - West Systems, MAS, uscomposites, 5050composites, etc. These resins are used all the time by people constructing composite aquariums - they are totally safe and appropriate for the work you are proposing.

All that said, why spend on epoxy resin only to load it up with sand? Why not just literally use concrete? It's safe, strong, cheap, and easy to work with. Search for the various DIY live rock threads to get some ideas.

[Servillius]

At this point the two reasons I'm avoiding concrete is that I a) understand it takes a long curing time, and b) feel like the epoxy and sand might give a better color and cleaner look. This is speculation on my part, so advice is always welcome.

[NanoReefWanabe]

in a couple months the colour of the piece will be a moot point as it will likely be covered in coraline algae anyway...

but you can use a white (base colour no pigments) stucco mix if you are worried about the colour...

[Servillius]

Hmm.... not a bad plan. Is any stucco mix safe? Do I mix it with coral sand? How long does it need to stay in water to cure completely? Do you have a good link with all the answers I'm bugging you for? :)

[der_wille_zur_macht]

Portland cement is available in pure white. But, honestly, the plain-jane Portland gives a pretty accurate color rendition of live rock. The final appearance will depend heavily on the aggregate you put in the cement - if you put sand and crushed coral in it, it'll look pretty much exactly like live rock in both color and texture. That's what most people who build DIY live rock do. There are many very good DIY rock threads in this forum, have a search and I'm sure you'll find them. All your questions are answered in great detail.

Curing time depends on several factors. At best, you'll be looking at a few weeks. It'll be "solid" in a day or two, but will not be fully cured for some time after that. IMHO it's still the best way to go if you're trying to build rock-like structures in the tank.

Have you totally abandoned the idea of using acrylic rod and plates? You can do that in an afternoon.

[BeanAnimal]

Mixing resin and sand to to get a barebottom tank with a sand bottom look (faux sandbed) is not new. However, you need to be very careful in hpw you plan your project.

It will be cheaper to mix sand and resin to create a thick mixture than it will be to pour the bottom of the tank and cover it, but that is not the issue you need to overcome. Different resins and epoxies have different shrinkage rates and different water absorbtion rates. That means that the resin will expand and contract at different rates compared to the glass. It will swell when exposed to water and shrink when dry. The heat generated during the curing of the resin can exacerbate the issue by expanding the glass as the resins cure and allowing them to shrink when the resin cools. The tight fit and solid bond between the glass and resin can create huge issue when the tank is filled. The Resin will absorb water and expand, cracking the tank!

There are several threads here with first hand experience showing the destruction caused by poorly planned faux sandbed installations! If you decide to pour a faux sandbed, then you need to prevent the resin from bonding to the tank and allow a buffer for expansion and contraction. Pouring the mixture onto a thin layer of plastic and leaving a small perimeter gap is a must.

I don't have time this morning to explain the pros and cons of epoxy vs poly resins, but a search of the internet and RC should yield all of the information you need.