Installing HDPE in Bare Bottom Tank Questions

[Fish Fan]

Hey all! I recently picked up an IM Nuvo Fusion AIO 25 Lagoon to be a coral and motile invert QT/Frag tank (fishless) to support a 150 display that I just ordered :-)

For a lot of reasons, I want to go bare bottom here, please don't try to talk me out of that lol ;-)

I ordered a piece of 1/4", black, HDPE to put under my rocks,

My question is, should I just cut the HDPE material to fit, put it in the tank, and then pile my rock on it? (I read that sometimes the HDPE floats?)

Or, should I try to silicon seal this in some way? I consider myself pretty good with silicon, but I DO NOT want some amateur looking silicon seam on the bottom of my brand new IM tank.

Plus, I don't want detritus getting under the HDPE plate, nor do I want critters like snails and crabs to get under there.

What do you guys suggest here?

Please know, I already have the IM Nuvo 25 AIO tank, and I already have the HDPE material. And, this is not my display tank ;-)

Any help or suggestions would be much appreciated!

Thank you in advance!

 

[Nano_Tuners]

I don’t silicone it down when I’ve used starboard in the past, with the rock on top it’s fine, and there have been times I made a mistake and would’ve been in a world of hurt if I had adhered it

 

[Fish Fan]

No worries about critters getting under there?

 

[dpoltsdsu]

I’ve used it and just stacked the rocks on top and it wasn’t an issue for me! I didn’t silicone it or anything like that

 

[Nano_Tuners]

No worries about critters getting under there?

Not as long as you’re starting with a clean bottom

 

[MoshJosh]

All my tanks are bare bottom but I just put my rock directly on the glass (keep in mind I use flat bottom rocks/base rock primarily). So for me I would skip the HDPE. If I HAD to use it, I would consider cutting it to the shape of my base rock so there was only plastic where there was rock. While I like the idea of siliconing it down to keep critters and detritus out, I fear the silicone will not adhere properly leading to its eventual failure (not really an issue as the rocks will hold it down but still sort of defeats the purpose). Also, keep in mind plastics can expand in water. I’m not sure how much with HDPE, but something to consider when you are sizing it.

 

[helmsreef]

Silicone won’t adhere very well to hpde, it’s usually mechanically installed. Any silicone you use will either not adhere or come off shortly down the road so just lay it down under your rocks.

 

[RedReefer]

No silicone for me.

 

[Fish Fan]

Hey guys, thanks for the replies! No silicon is what I wanted to hear because I don't want to mess with it lol!

Yes, this will be for a brand new tank, so nothing between the HDPE and the bottom glass.

@MoshJosh I do plan on machining some of my rocks to have a flat base, I do like that look, and think the rocks will be more stable that way. I thought the rock from BRS that's already cut flat way entirely too expensive (I get that you're paying for someone to cut it). I looked into in and many say you can cut rock yourself with a rip saw or angle grinder with the right blade, or even just a simple hand hack saw.

Thanks again, everyone!

 

[Fish Fan]

Also, I know this material is easy to cut, but I want to get a nice, clean fit and finish. How did some of you cut this stuff? Did anyone run it through a table saw, and if so, what blade did you use? I have a high-tooth blade for plywoods and melamine, and I think that may work well. Or, I could rough cut it and then make a pass with a router to clean up that edge nicely.

Any suggestions?

Thanks again for your help!

 

[Nano_Tuners]

It’s a soft plastic, Table saw with your existing blade will be fine. Move it fast to avoid melt

 

[danreef55]

I am going bare bottom but no HDPE. Joe from GlassCages advised against it. Did a bit of research and you shouldn't use sealant. I have flat bottoms on all my base pieces of rock so going to place it directly on the glass.

 

[Fish Fan]

I am going bare bottom but no HDPE. Joe from GlassCages advised against it. Did a bit of research and you shouldn't use sealant. I have flat bottoms on all my base pieces of rock so going to place it directly on the glass.

Thank you for the reply! Everything I saw said to use it, said to not put rocks directly on the glass bottom. Why did Joe say this? Is it because detritus gets under the plate? Is it something specific to his tanks?

 

[danreef55]

Thank you for the reply! Everything I saw said to use it, said to not put rocks directly on the glass bottom. Why did Joe say this? Is it because detritus gets under the plate? Is it something specific to his tanks?

Detritus and critters get under the HDPE which also can expand and contract nominally. @Joe Glass Cages can you please elaborate?

 

[Fish Fan]

Detritus and critters get under the HDPE which also can expand and contract nominally. @Joe Glass Cages can you please elaborate?

^This! I have been worried from the start that detritus would accumulate under the HDPE plate, or a snail or critter or would get in there and cause problems.

I don't want to try to silicon it in, it seems problematic, even if I'm pretty good with silicon.

I've spoken with Joe from Glass Cages before about a different build. He's a solid guy, who makes great tanks, and I aspire to own one!

For this build that I want currently, again, a frag tank, not my display tank, I learned how to cut dry rock so it sits as a flat piece on the bare bottom tank; I like that look.

If I can be one of those guys that can build and plan a rock scape outside of the tank, and I can be certain it won't tip over, maybe there's no reason for the HDPE, considering my rock will be glued in place.

Thank you for your help!

 

[danreef55]

You can do it too. seven separate structures interlaced

 

[Fish Fan]

Bump for if I need the HDPE or not lol!

Thanks guys!

 

[helmsreef]

Also, I know this material is easy to cut, but I want to get a nice, clean fit and finish. How did some of you cut this stuff? Did anyone run it through a table saw, and if so, what blade did you use? I have a high-tooth blade for plywoods and melamine, and I think that may work well. Or, I could rough cut it and then make a pass with a router to clean up that edge nicely.

Any suggestions?

Thanks again for your help!

I have used a high tooth count table saw and I also you can use a sharp razor blade and score it, then snap it over your knee.

 

[Fish Fan]

I have used a high tooth count table saw and I also you can use a sharp razor blade and score it, then snap it over your knee.

Thank you! You know, a lot of people I saw were using 1/2" HDPE, but for my humble 25 gallon build I thought 1/4" would be fine. And given that it's only !/4", I may be able to score it and snap it. That may actually be easier that trying to run it through the table saw.

But, now I'm wondering if I need it at all. I *believe* that the only reason to use it is to protect the bottom glass from scratches, or from potentially catastrophic failure if a rock was to fall (which I have a hard time imagining, though I have read that it has happened).

I'm not planning on any crazy NSA type aquascape, and I'm not artsy at all, but I am going to machine some of the base rocks to be flat, like the "shelf" rocks, so the base should be very stable. And, this tank is only 11.9" tall, so I'm not going to be building very high, and I do want to try to epoxy everything together, which should make it all very secure, kind of like @danreef55 did above.

I'm stating to think I may not need the HDPE in this tank at all. THought?

Thanks guys!

 

[Fish Fan]

@Joe Glass Cages I just noticed you reacted to a post here. If you're out there, I'd very much welcome your advice here :-)