What substrate should you put at the bottom of the axolotl tank?
Sand? Gravel? Nothing?
Today I'm going to open a big can of worms and dive into what has evolved into the highly controversial topic of substrates for axolotls.
Believe it or not...
... The substrate (or lack thereof) you choose has a HUGE impact on your entire experience with axolotls.
Not many people realize the substrate is more than a cosmetic touch when they start out setting up their tank.
It impacts so many things, including...
- Your aquarium's ecology
- Your water parameters
- Your axolotl's health
- Your workload
- And of course, aesthetics
Notice how I put aesthetics as the last element of the list... though it's usually the first thing (and sometimes the only thing) people think about.
(Trust me, I think about that part a lot too :) )
Generally speaking, most people just want to know two things: how it looks and how easy it is to keep clean, but as listed above, it's bigger than that.
Thoughts on Bare Bottom Tank Substrate
Okay, let's start with the bare minimum and talk about bare bottom tanks.
I will say this:
They can have their place in certain situations.
They aren't always bad.
For example, if an animal is sick and in a hospital tank or tub, having no substrate temporarily can be beneficial during treatment, as dissolved organics a substrate contains can work against some medicines.
Or as a breeder, sometimes it's required for frequent water changes on babies.
But for the average pet axolotl aquarium, for several reasons, I don't find it to be ideal.
Say you have a decent size aquarium with an axolotl or two.
We all know those axolotls are going to leave you some, eh, presents.
In a long-term setup, having no substrate might make it easier to suck up waste with a turkey baster or siphon on a daily basis.
But is that how you want to spend your time, hunting and pecking for each axolotl poop?
Firstly, WAY too much work. ;)
More importantly, trying to maintain "sterile" conditions by simply removing waste on a daily or weekly basis (no aquarium with animals is sterile, by the way) tends to foster the buildup of bad bacteria.
This can cause common issues such as cloudy water.
Funky tank smell.
Chronic fungal issues.
In worse cases, it can lead to bacterial infection, sometimes FATAL infection. :(
(Read more about why bacteria is possibly the greatest enemy of axolotls here.)
This is because there isn't enough probiotic bacteria to keep the bad ones in check because they lack the surface area they need to colonize.
These aren't the same as the nitrifying bacteria in the filter...
These are the other kinds of bacteria responsible for the well-being of your aquarium.
I have found it to be far more effective to stop trying to fight natural processes and start harnessing them to your advantage.
(More on that later.)
Not to mention...
Axolotls are called the "Mexican walking fish" for a reason.
But in a bare-bottom tank, once the axolotl gets bigger and starts throwing its weight around, they don't have much to grip on.
To combat this issue, some people install stuff like astro turf (I would NOT recommend - full of bad chemicals) or even rug anti-slip gripping pads at the bottom of their aquarium (likewise often made of synthetic chemicals and hard to weigh down and clean around).
Thoughts on Sand Bottom Substrate
"Is sand okay for an axolotl?"
It's a common question.
I used to use sand only for years, but I don't anymore.
It's really hard to clean if you are trying to vacuum it regularly; it tends to suck up in the hoses and clog.
Foreign particles start mixing in with the sand and giving it an off-color and/or strange looking patches, unless your sand is already pretty dark.
The axolotls also tend to stomp it around and move it a lot more and create bare spots at the bottom.
If you don't wash it a million times, it can give you issues with cloudy water, especially if the axolotl freaks out and starts kicking it everywhere when it gets startled.
Then, there are the health concerns.
There is some concern as to how safe it is for axolotls to be ingesting sand.
Some say they need to be at least 5 or 6 inches and then it's okay.
Then there are others that seem to keep them on sand at less than that size without issue, provided it is a fine grain sand.
Honestly, I can't say for sure either way on this, because due to all the other problems I have with sand I haven't bothered to intensively study its safety with lotls.
Plus, I have a system that works.
Why reinvent the wheel? :)
That's not to say it can't or doesn't work at all for others, but that's just been my experience, and when designing an aquarium, I want to mimic the species' natural environment as closely as possible.
"Sand only" substrate doesn't fit the bill for that, in my opinion.
Thoughts on Gravel Substrate for Axolotls
What is an axolotl owner to do?
If you've made it this far, you might be more open-minded than some people.
Everyone has their own opinions, but what are they based on?
Personally, I want to base my advice on two more reliable things than just an idea floating around or hearsay (which unfortunately is the case many times on social media, YouTube channels and online articles)...
Personal experience, and conclusive scientific backing.
For scientific backing, we can't point to a ton of studies either way, in support or against gravel, because they aren't really out there.
But we can look at the natural environment of the axolotl.
You may have heard this:
"The natural substrate of the axolotl in the wild is made of silt and mud."
"The natural substrate of the axolotl in the wild is sheer rock with nothing else."
Neither one of these appear to be accurate.
Just check out this article on axolotl habitats for more information.
As far as personal experience goes...
From early on in my axolotl days I've talked about so much of the needless fearmongering about gravel being harmful for axolotls and encouraged folks to think things through logically and scientifically.
After all this time...
I haven't changed my position.
I still use and recommend gravel with axolotls, and I still have had nothing but success with it.
Our sizeable breeding colony is kept on gravel, and they get nothing but the best.
And out of all those animals, after all this time, NOT ONE IMPACTION. :D
But it's not just me...
Other breeders, some keeping axolotls for over 30 years, follow similar methods with similar results.
Healthy axolotls that are strong, precise swimmers flourishing in a tank full of probiotic bacteria and beneficial microorganisms.
None of the animals in these systems have issues with the dreaded recurring fungus.
You may have heard some say,
"Gravel is messy because you have to vacuum it all the time."
Well, that's interesting, because I never vacuum my gravel.
I used to, back when I would use gravel only.
Yeah, it needed it, and yeah, it would get nasty without something like an undergravel filter, and yeah, it was a lot of work.
Too much work.
That's why I changed.
I stopped using gravel only and switched to a more bioactive deep layer substrate.
(You terrarium folks may have perked up at that.)
Yes, thanks to the amazing power of natural substrate and healthy live plants, my axolotl tanks are self-cleaning.
No ammonia, no nitrite, safe nitrate levels, no cloudy water, no smell, no hauling buckets, and most importantly...
This may have been a longer read, and there is definitely more to talk about when it comes to setting up a tank's substrate, but hopefully this got you thinking on ways you can make a better tank, both for you and your axolotl.
Thanks for reading!