What size gravel should I use in my goldfish aquarium?
The gravel substrate you choose is easily one of the biggest factors contributing to the overall visual appeal of your aquarium. Apart from colours and the substance the gravel is made from, size also plays a part.
Smaller sand based gravels give a tropical feel to the aquarium, pea sized gravel offers a more traditional setting and larger pebbles still can give you an aesthetically pleasing riverbed.
Focusing primarily on goldfish tank, here’s a run down on the pros and cons of the various sizes of gravel available for aquarium use.
Sand
by cjdevesa
Sand can be very pleasing to the eye in an aquarium. You know how some people put up those giant photos of exotic sandy beaches in their office to remind them they hate their jobs?
Same concept applies. A sandy oasis aquarium full of fish can be a wonderful escape to lose yourself in.
Unfortunately for goldfish, sand isn't so good.
Goldfish are notorious gravel pickers. They will eat all the food available and then charge headstrong into the gravel throwing it around everywhere searching for that elusive last morsel.
Sand, whilst small and in no danger of getting stuck in a goldfish's mouth does irritate the gills. Being so small it's easy for goldfish to throw it around and long term this gill irritation isn't healthy for your fish.
Cleaning can also be a bit of a pain with sand as the particles are so light they often get sucked up into your syphon along with all the crud. Goldfish produce a lot of crud which means it's probably not worth your time salvaging the sand mixed in with it at the bottom of the bucket.
Worse still if you're using a python, well the sand is going straight down the drain.
When keeping plants it is also possible to note that because sand is so fine and dense, it's actually possible to crush plant roots rather then support them.
Finally because sand is so fine it's possible that without adequate aeration (either via mixing up the substrate yourself or through plant roots), pockets of toxic gas can form in the sand.
Over time these turn anaerobic (lack of oxygen in the pocket) and hydrogen sulfide can be produced. When released, this gas is extremely toxic to fish should they expose one of these pockets via substrate digging.
Despite looking nice, I'd recommend staying away from aquarium sand for a goldfish tank.
2-3mm "pea sized" gravel
In a goldfish tank this sized gravel is my preferred choice and is the most widely available. Pea sized gravel is small enough to not pose a threat of getting stuck in your goldfish's mouth and large enough to avoid the problems associated with sand.
It can however be kind of boring if you stick with the standard colours, I think every beginner fish keeper starts off with the bog standard brown pea gravel. To get around this have a hunt around and see the various colours pea sized gravel is available in.
Personally I like to stick to the darker colours. I find this gives the most contrast between plants and fish and doesn't give off a glare into the water like lighter gravels do.
Oh and please please avoid the rainbow coloured fluro gravel. I don't know who's using this in their fish tanks but it looks horrible!
Pebbles
With pea sized gravel some people still worry about it getting caught in their goldfish's mouth so that's where pebble gravel comes into it. Pebble gravel is typically large enough to not fit into a goldfish's mouth entirely.
Available in various sizes from a 20c piece right up to large riverbed style pebbles, Pebble gravel makes a good choice for the fish keeper that wants to create a natural look but isn't looking to grow plants in the substrate.
Keep in mind that plants can still be grown in a pebble substrate tank but are typically grown in pots (a layer of soil covered by pea size gravel), which are then buried in the pebbles.
One drawback of the pebble substrate is that crud can very easily fall down between the pebbles. Being so large you don't have the compactness of smaller substrates so it's not uncommon for waste to simply fall through to the bottom of the tank.
When cleaning the tank with a syphon this can be tricky.
Another consideration is that if you keep smaller fish alongside larger fish it's highly unlikely but still possible that one of the smaller fish could get trapped under a pebble. My goldfish go crazy at dinnertime and it due to their size wouldn't take much to move pebbles around.
If a smaller bristlenose pleco happened to be hiding in one of these gaps well you can guess what might happen.
An additional option is to use pea sized gravel as your main substrate with pebbles on top to discourage fish digging into the gravel in specific areas, for example where plants are rooted.
When choosing your size being aware of these considerations will go a long way in maintaining the health of your fish and longevity of your aquarium.
August 30th, 2009 at 1:47 pm Suzie(Quote)
Fabulous article. I didn’t realise keeping goldfish could be complicated. We just used to keep them in an old bath outside.
August 30th, 2009 at 2:19 pm davepoole(Quote)
Im using ecocomplete black in my tropical tank. i did have a goldfish tank back in England that i used small rounded slate from the beach as a substrate. I cleaned it and soaked it well before going in. Looked great. Your tank is looking good, amazing to say it doesnt have filtration.