Today I want to talk about something that often gets overlooked in the hobby.
Water current.
What causes current?
- All electricity-driven filters
- Airstones
- Submersible pumps
So, how much current should goldfish have?
I truly believe that for them, the less current – the better.
This is interesting (from one of my older books on goldfish):
“One way, the most in use, although the worst for the retail customers, is to keep a steady stream of water constantly flowing through the tank. Now, this is wrong. Goldfish are intended to live in standing water, and should not be made accustomed to the contrary, as the reversing again of the character of the water often proves fatal to them. The proper way to keep fish is in pure standing water, to which the necessary oxygen is supplied by the action of aquatic plants…” (The Goldfish and Its Systematic Culture with a View to Profit,
Now:
Most pet store fish are born and raised in massive outdoor ponds with practically zero current.
They are then shipped to pet stores…
… Where they are blasted with strong water current from mega filter systems and simultaneously exposed to disease.
(This obviously is VERY stressful.)
Then they are put in a home fish tank with a power filter and maybe an airstone as well.
Some people even add a “wave maker” or underwater pump just to add even more current.
Any wonder that so many new fish die in a week just from the shock?
While some of the hardier goldfish may to adapt to this…
… It may not be ideal.
Many people may tell you that a 10x turnover flow rate is what you want for a filter.
While higher flow rates mean more efficient biological filtration…
… They can mean unhappy goldfish!
Many people say you can never have too much oxygen and filtration.
This is usually true.
But you CAN have too much current.
In the wild, their homes are stagnant ponds.
Other fish like the hillstream loach may appreciate more swift-flowing river-like conditions.
Generally, going back to the more natural habitat of the goldfish tends to yield better results with the species.
(Obviously keeping fish indoors there is going to be some inevitable difference.)
- If your fish stop swimming, they should not still be moving. Otherwise they are being blown around.
- If your fish seem to swim in place a bit when getting from point A to point B, it is a sign they are fighting the current
- If your fish sit at the bottom, they may be exhausted from struggling.
Fancy goldfish (especially with long fins) do not appreciate current.
The excessive finnage on fancy fish acts like a parachute, catching the water and pushing the fish all around the place.
Other experienced goldfish keepers also feel even their slim-bodied fish do much better with lower current.
- Decreased activity
- Exhaustion
- Stress
- Propensity to illness
- Collapsed fins
Even sponge filters create significant water current for a goldfish tank.
I’m not saying you should never use airstones, filters or pumps in your aquarium.
These things can all be used – but the current should be minimized.
How to Reduce Current
Airstones can be positioned near the surface with a small or adjustable air pump providing minimal push.
(Or an air control valve really helps.)
Filter outlets can be placed on the water level and undersized filters used instead of oversized ones (unless you have some way of mitigating the flow, such as using a sump).
Submersible pumps can have the flow rate manually turned down if they are designed to be adjustable.
(Though the more electricity-efficient method would be to get a lower-rated pump.)
You’d be surprised how much water turnover is really necessary for a good filter to function properly.
Especially if you couple it with live plants.
See:
Plants are the ultimate low-current water filter. 😉
And not only that…
… They oxygenate the water as well.
In some cases (when properly balanced), plant-only filtration can power an entire tank without the need for an electrical filter altogether.
Great for your wallet and your fish.
I mean, an electricity-driven filter may seem less expensive than buying live plants at first.
But over time, the energy bills usually dwarf the cost of the filter.
In fact:
People have been keeping fish for hundreds of years without them.
Not saying by any means this is the only good way to keep goldfish.
Only that if you use a mechanical filter that creates current, it’s something that might require a bit of fanangling.
Many fishkeepers have told me that simply reducing the filter current for their fish results in much more active fish – fish that before seemed like they were sick or afraid for no reason.
As always:
Monitoring the water quality is a good idea when turning down your filters.
This makes sure you don’t interrupt your biological cycle….
… Especially with high-turnover reliant filters such as Hang on Back filters.
If you find ammonia or nitrite, perhaps consider adding some live plants or a small sponge filter could be just the ticket to a low-current, well-balanced aquarium.
What About Good Circulation?
Some people worry that by reducing the current, you can create “dead spots” in the tank.
Lots of water flow ensures no dead spots.
Personally?
I don’t worry about dead spots.
Goldfish themselves constantly move through the water and forage, stirring up the debris on the bottom.
This alone seems to be ample activity to prevent dead spots in the water column itself.
Some fishkeepers (myself included) even purposely try to cultivate dead spots in the substrate to help with anaerobic filtration.
While this itself is an entirely different subject, my point is that I have yet to see any problems with dead spots.
As long as you have a decent amount of plants helping to oxygenate the water?
This really shouldn’t be an issue.
Final Thoughts
I’m sure not everyone agrees with me about current, and that there are many people who keep goldfish very successfully in stronger-flow tanks.
This is just what I have found works best for my fish…
… And what I have heard from talking with my readers.
So, want to chime in?
Speak your mind in the comments below!
Do you have any tips on convincing parents to let me get a goldfish for Christmas? I’m 15 and I think it’s a little silly my parents don’t think I’m responsible enough. I have read quite a few articles on this website and the more I read, the more I want a goldfish of my own! They think I will get upset if the fish dies (they think goldfish have the life expectancy of a fly). Any tips for me or my parents would be greatly appreciated!
Showing your parents you are responsible in other areas as well can help, like keeping room clean, doing homework, chores etc. You can also let them know you are willing to quarantine the fish properly to clean it up so it has a better chance of living a long time. Also getting it from a breeder gives you a much better shot at a long-lived fish 🙂
I’m setting up a 46 gallon bow front acrylic tank as a goldfish tank. These will be my first goldfish in many (many!) years, and I’m glad to learn more about filtration and current flow. Lots of things have changed in the past few years on this front. Planning to moderately plant the tank using your goldfish friendly planting tips (thanks!). I had already bought a big HOB filter, but I may swap it out for the lower powered one I had used on a 15 gallon tank so I have less flow. I’ll keep an eye on the water parameters, but I think with the amount of plants I have I should be good. Only planning on 4 small fancy fish for now.
Sounds really neat, Butch, keep us posted!
Hello! My parents bought my son for Christmas present a 16 liter tank with five goldfish!!! Now the weight is on me to keep them alive while doing a fish in cycle and trying to find a proper bigger tank for them. The tank came with a cleansys 200+ internal filter. Even at the lowest tip adjustment there was a current and the motor stressed. I saw videos and comments and more videos and more comments and came with the idea of taking a sponge and cutting it and fitting it on the tip of the filter that blows the water…. The current now in my opinion is perfect for the goldfish they seem relaxed and scavenging in the pebbles and seem to enjoy themselves! My problem now is that there is not enough ( in my opinion) surface movement for good oxygenation. Will they be ok with very little surface movement? I havent seen them gasping at the top more than before. Will there be any problem with the fish in cycle? This is the third week and have done a lot of mistakes…lets not talk about them…but i think im doing ok! This is the first day of the sponge on the filter so i dont have any results for anything. Im always confused and stressed and i “thank” my parents everyday for my son’s christmas present 🙂 sorry for talking this long! Love your blog by the way! 🙂
Most power filters create enough oxygen that you needn’t worry. Lots of folks do fish-in cycling. I have too. It can be done 🙂 Thanks for your kind words.
Like many novice goldfish owners I took the advice about 10x water turnover per hour and bought an oversized filter for my tank. The current really stressed out one of my fish, who happens to have has a smaller body and longer fins than the others. I tried turning the filter down, rearranging plants and decor, just about everything! What worked in the end was putting a cylindrical pre-filter sponge on the filter outlet. Now I can run it at full speed for maximum turnover, and all of my fish are much happier because the current is completely dispersed. Thanks for helping me figure out what the problem was!
Glad to hear that the post helped you, Adrian!
Hi Meredith. Is there your FaceBook Group I can join? I’m really interested to read about the available texts. Thanks.
Sure, you can check out Pure Goldfish Community or Nano Goldfish.
Mrs Clawson I loved your input on keeping goldfish. Hun I have a biocube 32 gallon. Would the return be a bit much I would like to keep 1 in the tank would you mind giving me a little of your personal but professional input. thank you kim
The flow may be considerably mitigated on these via the use of a sponge partially obstructing the overflow… have you given that a shot?
Just to say first: I love your website! I\’m a novice goldfish owner, but had decades of experience previously with tropical fish (so thankfully I had some idea of what I was doing!).
I have a 21 litre tank with one small Black Moor (I\’m upgrading to a 60 litre tank soon). I put in an underwater filter, and did a few mods on it to make the outflow not so strong. Moorie was a bit freaked out at first, but he got used to it and now I swear he enjoys it. When he gets bored he swims up to the output valve, dives in, goes for a ride, and he will do this a few times. It\’s like Mr. Road\’s Wild Ride, for fish.
Oh, and I\’ve ordered your book, it should be here soon.
Keep up the good work!
Thanks for sharing, T.H., and for your kind words! Your black moor sounds like he is enjoying life for sure!