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Growing plants in aquariums is so so good – the second best place to grow plants (the best being in a big terrarium).
It’s pretty easy to grow house plants in aquariums – they tend to come pre-lit, they’re naturally humid, you don’t need to water, and the fish provide the fertiliser. The only difficult thing is working out how to keep the leaves out of the water.
If you have any specific questions, leave me a comment.
Most plants will grow in water, but stay away from any plants that don’t like humidity, such as cacti. Christmas cacti can do pretty well though, and they bloom more reliably than ‘dry’ cacti.
I’m just gonna go ahead and make sure that everyone knows we’re talking about freshwater fish. Don’t put plants in a marine set up – they will simply pass away.
You can put plants in goldfish tanks, but they will eat them. Goldfish are greedy, greedy pigs. A lot of people also advise against keeping house plants in with angelfish because they eat the roots, but we had 8 big angels in our last tank, and my Thai Constellation roots went unmunched.
It goes without saying that our aquarium didn’t have a lid. Some fish need a lid on the aquarium because they jump out, but none of ours did (excluding the embarrassing incident when a powerhead was round the wrong way and was yeeting mountain minnows onto the floor – luckily we were there to intervene).
If you want house plants in the aquarium and have jumpy fish, you’ll have to lower the water level (providing the fish would have enough space) or get a bigger tank.
Clean the roots off well
Cleaning off the roots well is important when putting plants in water, and even more so when they’re going into an aquarium. Soil can contain microbes and nasties that could potentially harm your plant.
If you have a specific plant that you want to grow in your aquarium but you can get the roots clean enough, take a cutting and root it in the tank. I know it can be annoying to not get *exactly* what you wanted, but you don’t want to risk your fish.
Plants root really quickly in aquariums – especially tropical ones – because they naturally combine all the elements required for rooting cuttings in water quickly. The water is well aerated, warm, clean, and it’s humid. PERFECT.
Make sure they have enough light
Light can be an issue with aquariums because if you have big plants, the lights will be below the plant. You might think that that’s ok, because there’s ample natural light in the room BUT sometimes plants get a bit ‘but I want to grow towards THAT light’ and end up curling under a grow light and inevitably both burning and falling into the water and rotting.
I would recommend you clip a couple of grow lights on the back of the tank that are taller than your plants. Or have trailing plants like pothos that grow wherever they damn like.
Peace lilies actually grow really well in aquariums and tend to grow up, rather towards the light.
Select the right species
As I said before, most plants will do well in aquariums unless they hate high humidity, but some are physically more suited to it than others.
You CAN grow a rubber plant in water, but it’d be a pain keeping it upright in an aquarium.
If you’re new to adding house plants to fish tanks, then start with something that trails. A pothos, or a rhaphidophora tetrasperma will be good to start with. Also syngoniums and Philodendrons. Over time, you’ll notice holes appearing your plantscape, and you can add plants to fill the space.
The hardest thing is keeping the plants upright. For large plants, it’s usually best to anchor them properly. We stuck my Thai constellation in a big piece (shown below in my terrarium, which was once an aquarium).
Another great option is a Fittonia, mainly because they’re so easy to grow in water, but so hard to grow in dry environments. Set yourself up for success, you know?
Don’t submerge house plants in an aquarium
There are some plants, like Monstera adansonii, that you can submerge, BUT it’s not as easy as sticking the plant under water and be done with it.
I don’t actually know the process of submerging an adansonii but I know that it’s not that easy, and you will inevitably lose some plants to rot. I would highly recommend submerging it in a separate vessel of water, because we don’t want rot in the tank.
Most house plant leaves will rot. You need to keep them out of the water. I sit mine on bogwood, but you can also float them in slices of pool noodle, or stack rocks (make sure they’re secured with aquarium safe glue, and aren’t going to trap your fish).
Can you put Monstera in an aquarium?
My Monstera LOVED growing in the aquarium, and grew like a freaking weed.
That being said, Monstera do have a bit of a habit of growing a tonne of roots if they feel like they have the room, which is why I had the majority of my Monstera’s roots in the bogwood (it was hollow in the middle). They shouldn’t grow to fill the aquarium (though don’t quote me on that!) but you may see a lot of root growth before leaf growth when you first switch it over.
I personally think Monstera look quite cool trailing out of fish tanks. You may not get enormous leaves (unless you have supplementary light) but they look really, er, jungley. in a good way.
Do plants filter aquarium water?
Technically plants do filter aquarium water, and we do have a tank that relies on plants for filtration*.
You can only keep VERY SPECIFIC types of fish in these setups, and I wouldn’t want a fish relying on plants for filtration. Plants change and grow and die and they’re not as reliable as a *proper* filter. It works in the wild because there are a lot more plants and other elements that help keep rivers clean.
* This tank has one fish (named Baby Fish because we just found a random fry one morning) and he’s a type of killifish from, er, somewhere cold.
In the wild, they live in puddles that freeze over, so as you can imagine, he’s pretty hardy. He doesn’t need a filter at all (tbf he could probs live in a manky pint glass) and he can’t have any friends because he’d kill them. He is pretty though.
Do house plants like fish tank water?
Yes! At least, I’ve never met one that didn’t. I’ve written an article here on watering house plants with aquarium water if you’re interested.
Aquarium water comes naturally fertilised, dechlorinated, aerated, and room temperature (or a bit warmer).
Bear in mind that your filter will be removing a lot of fish poop from the water, so when you’re cleaning the filter out, add the gunk to your caddy of aquarium water. We also add nutrients to the water for the aquatic plants – I don’t think they particularly benefited the house plants, but they didn’t seem to hinder them at all.
Definitely give growing house plants in your fish tank a go – or at the very least, propagating them. The conditions are great for them, and you don’t need to remember to water or fertilise them!