# Plywood inside aquarium to support branches?



## Andrew Butler (13 Dec 2017)

I'm looking at a way of securing some pieces of wood so they stand either a bit more rigid or upright. I've read about people using a plywood base inside the aquarium and gluing / screwing the wood to it.

Does anyone have any light to shed on this?
-I would only use true marine plywood.
-People use glue guns, is this glue safe?
-As for screwing I'm unsure about this, maybe while the glue cures but decent stainless steel screws seem hard to come by I find.

Cheers
Andrew


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## Tim Harrison (13 Dec 2017)

Marcel @zozo is your man https://www.ukaps.org/forum/threads/henry-goes-steampunk.50976/


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## ian_m (13 Dec 2017)

Andrew Butler said:


> I've read about people using a plywood base inside the aquarium and gluing / screwing the wood to it.


I wouldn't put plywood, even marine ply, in a tank. Waterproof ply is waterproof but certainly not waterproof enough to withstand constant immersion. Could coat it in fiberglass, like people do when making plywood tanks, but I think going a bit OTT.

Why not screw the wood to a piece of slate or a pebble ? Drill a hole in a suitably sized piece of slate or pebble, put a stainless screw through it into the wood. Add some aquarium safe silicone to stop it moving. Place in tank, cover slate/pebble with substrate. Done.

Stainless steel screws are available easily on Ebay (for 1's or 2's) and Screwfix in packs of 100/200 for £10 odd.

Biggest issue is if you don't like the wood placement or wood gets covered in algae, not easy to remove/move as fixed in place.

Personally I would soak the wood for months so get it saturated so it sinks by itself. Boiling can help speed up soaking. Or, as I have done, hollow out non visible areas of the wood, drill holes and chisel and stuff full of lead plant weights. Plant weights can come from either plants you have bought or Ebay. Maybe even put a stainless screw to hold weights in. I used hot glue, but after a couple of years hot glue does work its way loose from wood


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## Tim Harrison (13 Dec 2017)

Okay, should have taken the time to read your question properly, just saw plywood and aquarium and thought the obvious. 
Hot glue also works well, and is safe to use, but the wood needs to be clean and dry.


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## zozo (13 Dec 2017)

Hi,


Andrew Butler said:


> securing some pieces of wood so they stand either a bit more rigid or upright.



You intend to make a base stand bellow the substrate so to wood is secured in a upright position. Than i wouldn't go for plywood, not even marine plywood. anything wood needs to be coated, even if you use marine plywood or concrete plywood etc. As far is i know it's only surface treated, bt if you saw it than the sides are still untreaded wood. Than you have to apply epoxy coating.. This also means if you drill it, you drill into the bare wood, if water gets into this hole the wood will suck up wate rfrom the inside out.

Acrylic panels can be used as flat base, if you give the acrylic a good rub with coarse sand paper than silicone stil sticks fairly good to it. So if you have figured out the permanent place you can kit the acrylic to the glass bottom panel. Or use bakked red clay tiles (terracotta) to get some weight to it.. Even PVC can be used and is available in sheet material.

You indeed could use stainless steel screws, but if these are to hard to get for you. You can use counter sunk nylon metric screws as well, In hard wood these usealy isn't a problem and tap metric thread into wood is easy how harder the wood how better it holds. It doesn't need to hold an elephant, does it.  Take the screw as long as possible, say 40mm and tap it's intire length of thread into the wood with a M6 metric tap you can put the tap in the cordles dril.. After the wood is threaded put silicone kit in the hole and screw the wood to the plate.


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## tam (13 Dec 2017)

I did this recently, and used egg crate and cable ties. You can see the result here: https://www.ukaps.org/forum/threads/planted-tank-for-catfish.51350/#post-505005


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## Andrew Butler (13 Dec 2017)

What I'm trying to do is using some Azalea root or fingerwood cut a flat spot and be able to stand the pieces up at interesting angles without having to rely on the shape or weight of the wood to do so and also without it resting on the side pieces of glass. I'm looking to have quite a flat bottom which I can put some pebbles on to give it a riverbed type look like in Lauris 'escape'
https://www.ukaps.org/forum/threads/escape.40308/

I do still like the idea of using a piece of ply but don't want to risk it, if only I could find the thread where it was used.



ian_m said:


> I wouldn't put plywood, even marine ply, in a tank. Waterproof ply is waterproof but certainly not waterproof enough to withstand constant immersion. Could coat it in fiberglass, like people do when making plywood tanks, but I think going a bit OTT.
> 
> Why not screw the wood to a piece of slate or a pebble ? Drill a hole in a suitably sized piece of slate or pebble, put a stainless screw through it into the wood. Add some aquarium safe silicone to stop it moving. Place in tank, cover slate/pebble with substrate. Done.
> 
> ...



Marine ply isn't waterproof; it just uses different glues, is of solid construction so no gaps or filler and the wood isn't treated so it's just like a piece of natural hardwood with glues that shouldn't delaminate - unless you know different?

I had thought about using a slate flooring tile but wood is just easier to drill and fix together, I might look at going down that road if everyone's saying it's a no with good reason. Also no risk of cracking a piece of ply!

I can source stainless steel screws easy enough and have some but getting ones that are of a decent quality is hard; the ones from screwfix will show signs of rust if you leave them outside for a few months. Have you used some stainless screws without signs of rust? If so which ones?

I would have to make sure I liked the wood placement before things were finally glued and screwed!

It's not the fact it floats Ian, I intend to soak it regardless but trying to keep a piece of wood firmly in place I don't think is an easy task unless you can find those couple of pieces of wood that seemingly magically fuse together which I have given up on. I'm looking for the base fixing to support the wood with the fixing so I can put pieces off balance etc.

Aquarium safe silicone is of course a good option instead of hot glue, noted.



zozo said:


> i wouldn't go for plywood, not even marine plywood. anything wood needs to be coated



I hadn't planned to coat the azalea root / finger wood which I was going to fix to the plywood so why does anything wooden need to be coated?



zozo said:


> As far is i know it's only surface treated



Marine ply isn't treated with anything; it's just a tropical hardwood and glue, 'concrete ply' or shuttering ply is completely different and is full of filler to make it flat and not hardwood throughout. There's lots of different grades of plywood using different glues and constructions but a true marine ply is of the best construction and the price reflects that.



tam said:


> I did this recently, and used egg crate and cable ties


Thanks Tam but wouldn't work for what I'm trying to do

If anyone thinks they have a true knowledge about marine ply then please speak up.
Reading back some of my comments they come across as a bit rude which isn't my intention so sorry if it seems that way!


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## zozo (13 Dec 2017)

Andrew Butler said:


> plywood so why does anything wooden need to be coated?


You got a point there, if you would use untreated hardwood like oak or maybe teak there shouldn't be a problem with mounting any dw to a plank of this and soak it to make it sink. Than the only question is, why, it can be done much cheaper with other simpler to process inert materials.

Soft wood and plywood is a different story, pine will rot away rather soon and likely not very healthy, as far as i know soft woods leaches things into water you don't want. Plywood is as you say pressed and glued layers, if that soaks it expands, cracks and loosens.. I personaly do not know marine plywood, we do not use this term. Tho we have moist resistant plywood and concrete plywood.. So i assume Moist resistant likely is the what you call Marine version, its impregnated to repell water and concreteplex is epoxy coated, but not on the head ends when where it's cut. Anyway if you want to use anything not suitable for permanent submersion, the only way is to coat it to make it 100% waterproof. Problem is, like that it will never stay on the bottom. If marine plywood is exclusively constructed from hardwood in every layer, than likely the glue aint realy what you want in the water. If this soaks it finaly will expand and crack and let lose.


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## foxfish (13 Dec 2017)

Well there is lots of different grades of marine ply, my locale builders merchant sells a pretty poor grade but the boat yards sell better ones.
I learnt my trade as a boat builder & in those days we used real named plywood like teak & mahogany!
Anyway from my experience marine ply will last around 2-4 years when permanently  submerged & about one year if it is submerged & dried on a daily basis.
In the early day of koi pond building, we used marine ply for the filter bases & baffles. Even though we painted the components with G4 polyurethane, they would show sings of delaminating after around 12-18 months.
As a keen fisherman I have set crab pots for 50 years & can tell you that marine ply flaps & toggles last around 6-10 months.


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## Andrew Butler (13 Dec 2017)

zozo said:


> You got a point there, if you would use untreated hardwood like oak or maybe teak there shouldn't be a problem with mounting any dw to a plank of this and soak it to make it sink. Than the only question is, why, it can be done much cheaper with other simpler to process inert materials.
> 
> Soft wood and plywood is a different story, pine will rot away rather soon and likely not very healthy, as far as i know soft woods leaches things into water you don't want. Plywood is as you say pressed and glued layers, if that soaks it expands, cracks and loosens.. I personaly do not know marine plywood, we do not use this term. Tho we have moist resistant plywood and concrete plywood.. So i assume Moist resistant likely is the what you call Marine version, its impregnated to repell water and concreteplex is epoxy coated, but not on the head ends when where it's cut. Anyway if you want to use anything not suitable for permanent submersion, the only way is to coat it to make it 100% waterproof. Problem is, like that it will never stay on the bottom.


Softwoods contain much more sap which is the main problem aside from them rotting quicker, there are also hardwoods which are toxic to fish but this list varies dependant upon where you read. There are as I say lots of different grades of ply and there are moisture resistant plywoods lower down the price range than marine ply, shuttering ply or what I assume you call concrete ply is.



foxfish said:


> Well there is lots of different grades of marine ply, my locale builders merchant sells a pretty poor grade but the boat yards sell better ones.
> I learnt my trade as a boat builder & in those days we used real named plywood like teak & mahogany!
> Anyway from my experience marine ply will last around 2-4 years when permanently  submerged & about one year if it is submerged & dried on a daily basis.
> In the early day of koi pond building, we used marine ply for the filter bases & baffles. Even though we painted the components with G4 polyurethane, they would show sings of delaminating after around 12-18 months.
> As a keen fisherman I have set crab pots for 50 years & can tell you that marine ply flaps & toggles last around 6-10 months.


There are lots of different grades but true marine ply should meet BS1088, the reason many others don't is as they aren't completely solid inside meaning the cost can be greatly reduced - just look at the price of marine ply these days. Everything I've come across in recent years is a tropical hardwood of some kind or another. I've never seen delaminating of a marine ply, the wood has always rotted away first. Saltwater does have a different effect on the product though. Thanks for the input.

I'm getting pushed more towards a slate floor tile drilled, silicone between slate and wood and try harder to find some decent true stainless steel screws - think I'll have to track the code down.


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## tam (13 Dec 2017)

Is it pointy wood you want to go straight up? For those bits we cut a X out of the egg crate and stacked several deep to slot the wood in - only works if substrate is deep enough. Could you slice up some chunky bog wood and use that as a root proof/aquarium safe wood base that was easy to drill?


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## Andrew Butler (13 Dec 2017)

tam said:


> Is it pointy wood you want to go straight up? For those bits we cut a X out of the egg crate and stacked several deep to slot the wood in - only works if substrate is deep enough. Could you slice up some chunky bog wood and use that as a root proof/aquarium safe wood base that was easy to drill?


It wouldn't work for me as I'm trying to keep my substrate to a minimum.
I know I can get over it using a slate floor tile drilled if I can source some high grade stainless steel screws.


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## zozo (13 Dec 2017)

Andrew Butler said:


> There are as I say lots of different grades of ply and there are moisture resistant plywoods lower down the price range than marine ply, shuttering ply or what I assume you call concrete ply is.



Yes indeed shuttering ply probably is the same as concrete ply.. The ply used for casting concrete constructions. When i looked it up in english i found the term concrete ply.. So i thought it was a valid english name. My native language isn't english and in my language different terms are used for same products. We have hardwood ply and also water resistant hardwood ply, the last one i guess is what you call marine ply. Anyway, i've used plywood in a few accasions to build fishtanks and for this if coated properly it works like a treat..  And i did my fair share of investigation on the subject on different kinds of plywood and water. In the end there doesn't excist a plywood that is permanently water resintant all delaminate over time if constanlty in contatct with water simply because it still soakes water up. it's a natural process making it fanaly delaminate.

The glue used for plywood is still under debate and investigation in how hazardous it is on the long term whit gassing off in the atmosphere. Yet no proof found if it is unhealthy for building construction use. But it still gasses off quite some time after production. How this wil react in a closed aqautic environment is not investigated, i guess simply because even if it is hardwood isn't suitable for this kind of construction. There is no data to find about it.

Only thing i can find it's Phenol Formaldehyde  fully cured relative inert, but fully cured is also a relative concept because it still gasses off some time.
http://www.roseburg.com/UserFiles/Library/APA_Tech_Bulletin_on_Formadehyde.pdf

Formaldehyde seems to kill bacteria in an aquatic environment..
http://www.theaquariumwiki.com/wiki/Formaldehyde

So after all relativity, rather be safe than sorry with using it untreated in a fishtank.

Yes slate and stainles steel would be a beter option.


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## tam (13 Dec 2017)

Veterinary supplies? They would have medical grade stainless/titanium screws - don't know how much they'd set you back though. You can get plastic screws, might be able to use them with glue as more of a dowel.


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## Andrew Butler (14 Dec 2017)

zozo said:


> Yes slate and stainles steel would be a beter option


Getting a bit technical and no one really knows the answer so I think so.



tam said:


> Veterinary supplies? They would have medical grade stainless/titanium screws - don't know how much they'd set you back though. You can get plastic screws, might be able to use them with glue as more of a dowel.


The ones at the vets would be bolts, I want a wood screw so it holds. Marcel mentions using a tap to put a thread in the wood but it isn't all that dense and the thread on a bolt is very different to a wood screw.
Thanks for the input though.


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## zozo (14 Dec 2017)

Andrew Butler said:


> I've read about people using a plywood base inside the aquarium and gluing / screwing the wood to it.



What did they have to say about it?

In my personal experience, i glued a lot of drifwood pieces together in several tanks. And it only works temporary whatever glue is used. It all comes lose after a while. No idea if it is weeks or months because i didn't feel every day. The answer why is pretty obvious if you think about it, wood soakes and slowly degrades gets soft an disolves into the water collunm. 1/100 of a mm a month is enough for the glew which only addheres to the surface to let lose from this mean while soft surface it is on. It's best practice to glue epiphytic plants at the same glued intersections. Than the roots growen to both pieces of wood still holds it relatively good together. If not and gravity allows it it will fall apart.. That's an experienced answer i can give you about glue on wood submersed.

Obviously if you want to believe it or not, plywood is glued, if you want it to stay down it still needs to soak up water. If it doesn't it will float till the end of times. If it soakes water, the same process of degration will occur in the soaked wood. It slowly degrades and getting soft. Same story with the glue between the layers.

I've asked a professional if i could use High Presure Lamitate panels submersed.. It is 10 times harder and denser than plywood. You need HSS tools to machine it. The answers was No! It will finaly delaminate.


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## Andrew Butler (14 Dec 2017)

zozo said:


> What did they have to say about it?


I can't find the thread and not sure it was on here, they had just used it as I described - a flat panel at the base then screwed and glued the pieces of wood to stand up although in the case I read they were vertical pieces to imitate tree trunks.

I'm not going to get into an argument about these things; if you read back through my posts I think you will find I never questioned the fact that plywood is glued, infact quite the opposite


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## tam (14 Dec 2017)

Andrew Butler said:


> The ones at the vets would be bolts, I want a wood screw so it holds. Marcel mentions using a tap to put a thread in the wood but it isn't all that dense and the thread on a bolt is very different to a wood screw.
> Thanks for the input though.



My definition of a bolt would be flat ended to go with a nut? Vets use screws (have a pointy end) to go into bone. I admit I have no idea the different between a self tapping wood screw and a self tapping bone screw, but here is what I mean: https://www.orthomed.co.uk/category/internal-fixation/


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## Andrew Butler (14 Dec 2017)

tam said:


> My definition of a bolt would be flat ended to go with a nut? Vets use screws (have a pointy end) to go into bone. I admit I have no idea the different between a self tapping wood screw and a self tapping bone screw, but here is what I mean: https://www.orthomed.co.uk/category/internal-fixation/


I'd not come across titanium screws before; I just thought they bolted things, it turns out I'm wrong. I might have a look into this then so thanks for the info tam.


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