Plastic that Sinks

I'm currently making small decorations/objects/caves/etc for fish tanks using ABS (as PLA I believe dissolves in water) - but there's been one issue - it floats. We're looking at putting lead into each object, but so far that's been a bit pricey/time-consuming.

Are there any printed plastics that will sink in water (without having to sit in the water a few days first)? If so, what are the highest quality ones you know of and at what prices? Because these decorations will be for sale at low prices, unfortunately I've not had much opportunity to explore the more expensive options (eg Taulman branded), but will do if they prove to be the best option.


Also, does using Acetone vapour on prints increase or decrease the strength at all? I'm really struggling with small ABS parts (especially things that join together) that break apart when any pressure is applied to them and need to somehow strengthen them. These may be ridiculous questions, so my apologies (and thanks) in advance :confused:

Why don't you make a cavity and fill it with sand ? ?

You could use some of the pla's (does not dissolve in water) with added metals. They vary from 1.5-4 x the density of normal pla.

Pla is technically biodegradable. But for that to happen it needs to be in a hot compost heat with the right moisture. temperature and bacterial levels.

I live in england and have many pla items outside - if they were water soluble - trust me - this winter, they'd have dissolved :-)

I think there's another issue you haven't considered - ABS is toxic to fish (not as bad as the resins used in SLA printing, though): http://hackaday.com/2015/11/11/are-y...-prints-toxic/

Oh by the way, I made a boat in PLA for a pool.... still hasn't dissolved.

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Originally Posted by Tetraodon

I'm currently making small decorations/objects/caves/etc for fish tanks using ABS (as PLA I believe dissolves in water) - but there's been one issue - it floats. We're looking at putting lead into each object, but so far that's been a bit pricey/time-consuming.

Are there any printed plastics that will sink in water (without having to sit in the water a few days first)? If so, what are the highest quality ones you know of and at what prices? Because these decorations will be for sale at low prices, unfortunately I've not had much opportunity to explore the more expensive options (eg Taulman branded), but will do if they prove to be the best option.


Also, does using Acetone vapour on prints increase or decrease the strength at all? I'm really struggling with small ABS parts (especially things that join together) that break apart when any pressure is applied to them and need to somehow strengthen them. These may be ridiculous questions, so my apologies (and thanks) in advance :confused:

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If you want your fish to live, don't put lead in the decorations to keep them weighted.

I would personally print the item, make a simple mould and cast it in resin or something solid, that's your best bet for having something heavy that won't kill your fish from lead poisoning.

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Why don't you make a cavity and fill it with sand ? ?

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I hadn't thought of that - will have to check to see how much sand is required to sink the parts, but that might just work :)

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You could use some of the pla's (does not dissolve in water) with added metals. They vary from 1.5-4 x the density of normal pla.

Pla is technically biodegradable. But for that to happen it needs to be in a hot compost heat with the right moisture. temperature and bacterial levels.


I live in england and have many pla items outside - if they were water soluble - trust me - this winter, they'd have dissolved :-)

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I honestly haven't tested PLA in my tanks however I read that it was more soluble in waters with higher carbonate hardness (mine is very soft) so wasn't sure whether I would get different results. Heavy metals can be pretty toxic to fish but I'll look at what added metals they have - I certainly wouldn't mind moving to PLA as it's easier to print with.

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I think there's another issue you haven't considered - ABS is toxic to fish (not as bad as the resins used in SLA printing, though): http://hackaday.com/2015/11/11/are-y...-prints-toxic/

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Do they say what in the ABS is toxic? I believe ABS is the same material used for LEGOs which are definitely fish-safe, but obviously 3D printing is a different process. I have printed parts in most of my tanks (and have had for some months) with no ill effects & healthy fry, and am printing in the same room as the fish - however that definitely isn't a scientific process so if the stuff out of the printer is a genuine issue I'll definitely change. I had tried some research prior to getting the printer and couldn't find much on toxicity (but had read of others using ABS without issues) - the link came out well after I got my printer so naturally I wouldn't have seen it in time.

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Oh by the way, I made a boat in PLA for a pool.... still hasn't dissolved.

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Hmm - definitely worth me trying the PLA then :) I can't really wait 12+ months to see whether it has any issues at the moment so will continue with the ABS (unless the above part about toxicity is true, of course) in the mean time, though.

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If you want your fish to live, don't put lead in the decorations to keep them weighted.

I would personally print the item, make a simple mould and cast it in resin or something solid, that's your best bet for having something heavy that won't kill your fish from lead poisoning.

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Admittedly I have poor understanding of chemistry, but read that Lead was insoluble in water - will look into that further (lead weights were commonly used among fishkeepers for plants, however I believe alloys are now used instead).

RE Resin - I honestly wouldn't know what to cast it in. Price is a big factor for us and admittedly the 3D printing alone is still new to me. But if you have any ideas of where to start I'd be more than happy to consider a different route :)


Thanks heaps for all of the replies, by the way!

lead is not soluble - but lead particles will get into the tank.
lead water pipes are bow banned in the uk - because they put lead particles into the water supply.

Look at some of the pla with metal powder included wither as a colourant or so you can polish and sand them after printing.
brass, copper, iron - should all be fishtank safe.

The solubility of metallic lead (and its related oxidation products) depends on the ph of the water it's in contact with. If the ph is high enough, the lead won't dissolve, but if it drops below a certain point, then lead ions go into the solution. That is what happened recently in Flint Michigan, causing a major public health emergency. See http://cen.acs.org/articles/94/i7/Le...Tap-Water.html

So I have a simple solution... why not use 100 percent infill? granted the sand option might be cheaper on plastic. Both are great ideas in my opinion.

Anyone know of a way to make a 3d print float like a living fish? I want my 3d printed skeleton fish to float like a living fish does. you know, floating but submerged halfway to the bottom of the tank? Heck, different buoyancy levels for different skeleton fish would be super neat.Any Ideas? I'm new here so any ideas or help I can get would be great.