Increasing flow rate

[Country joe]

I had an email from aqua essentials a plant selling company, on how to control algae, they had a few suggestions, but one was poor water circulation, stating one filter is never enough, and plants should sway in the current,I should say this company does not sell aquarium equipment only plants, long scissors and forceps. So they are not trying to sell me a product.
My 200 litre aquarium the flow is powered by a Fluval 307 external filter, so I was looking at a Superfish IQ Submersible pump, 200 litres per hour adjustable. Not expensive to buy, would it be beneficial to add to my tank. My fish are mainly small tetras, Harlequin Rasboras, pandacorys and ottos, and one gourami.

 

[jaylach]

Depends on the fish population. Do the fish in the tank like fast or calm water. Put fish that like calm water in a tank with a high flow and it will cause stress. The reverse can also be true. As an example a tank I'm putting together (21 gallon) will have, through 4 air risers for under gravel filtration, the capability to move 300+ gallons per hour but my main fish will be Panda Garra which like fast water.

 

[MattW]

I myself have been guilty of putting the plant's needs over fish previously, and it will probably happen again. I love overgrown tanks. But I would suggest always to put the fish's needs first. I don't know much about the species you keep and whether or not they like high or low-flow but wait for some other responses or do a little research yourself

 

[Country joe]

I did think I have enough flow from my filter I know the flow rate that companies state are not truly accurate ,but my Fluval 307 states 40- 70 US gallons, 90 litres-330 litres, .and I have a 200 litre tank.

 

[jaylach]

On the surface I'd think 40- 70 US gallons 90 litres-330 liters per hour pretty low in a 200 liter tank. You are only getting around 1.5 full water volume per hour through the filter at its max of 330 liter/hour. I'd consider that pretty low.

 

[GaryE]

My fish are mainly small tetras, Harlequin Rasboras, pandacorys and ottos, and one gourami.

Small tetras is too vague to be able to comment.
Harleqins seem to like medium water flow.
Panda Corys are good with quick water. Corys move through a lot of different habitats.
Otocinclus are often fastwater fish, from high oxygen floating meadows.
Most gouramis like slower water, but not all.

Even within a group (tetras, gouramis) you'll have species by species differences.

@jaylach stopped me there and made me think. The fluval filter is giving you minimal turnover. Why not add another filter, rather than a simple pump?
I'd consider 5 times the volume of the tank per hour to be pretty moderate. That shouldn't bother the fish much.

You may have guessed I like moving water in my tanks, and I find I still get algae - just different algae then in tanks for slow water species. I get less hair algae, but other types keep on coming. I'm guilty of over lighting, since the room where I have my tanks gets natural light at this time of year, when there are no leaves on the trees.

 

[Magnum Man]

I think the subject worthy of more discussion & study... most of my tanks are higher flowing... I don't have algae issues, even on tanks that have 2 full length LED aquarium lights ( & my lights are on my schedule, so ( jaws drop ) my lights on my tanks, are all on 18 hours a day... I have one blackwater tank, with a slow growing Anubis in it, that gets some algae on the broad leaves... Oto's are pretty good at keeping the leaves clear, but I also incorporate some floating plants, over the Anubis, to keep everything in check...
algae loves the nutrients available in most aquariums...
I use a couple different kinds of terrestrial plants, growing out of the aquarium... it takes a while for these to jump into vigorous growth, but once they do, they seem to pull what the algae's need out of the water, so once those plants are mature, I rarely even need to scrape glass anymore... it may take 6 months or more, for them to reach this stage... also this vegetation, can be used to shade the aquarium, instead of floating plants, by moving the light above the cover several inches, and allowing portions of the plants, to grow between the glass & the light...

 

[Country joe]

Small tetras is too vague to be able to comment.
Harleqins seem to like medium water flow.
Panda Corys are good with quick water. Corys move through a lot of different habitats.
Otocinclus are often fastwater fish, from high oxygen floating meadows.
Most gouramis like slower water, but not all.

Even within a group (tetras, gouramis) you'll have species by species differences.

@jaylach stopped me there and made me think. The fluval filter is giving you minimal turnover. Why not add another filter, rather than a simple pump?
I'd consider 5 times the volume of the tank per hour to be pretty moderate. That shouldn't bother the fish much.

You may have guessed I like moving water in my tanks, and I find I still get algae - just different algae then in tanks for slow water species. I get less hair algae, but other types keep on coming. I'm guilty of over lighting, since the room where I have my tanks gets natural light at this time of year, when there are no leaves on the trees.

I have neon green tetras, black Phantom, tetras, black neon and glowlight tetras, Harlequin Rasboras, panda corys, and ottos, and one thick lipped gourami.
I have a small fluval mini filter, 45 litre, 12 US gallons, sitting in a cupboard doing nothing, maybe would be useful in the tank

 

[jaylach]

I would agree with @GaryE that 5 water turnovers per hour would be a pretty good rate for most community tanks. With the tank I'm putting together I'm going much higher than that but the main fish, Panda Garra, like fast water. I'll be aiming at around 10-12 water turnovers per hour but that is fish specific. For instance I was considering Ember Tetras as a shoaling fish to go along with the Pandas but the Tetras would not be very happy with the flow rate as they like a much lower water flow. If I were to run everything at max I would get around 15-17 water turnovers per hour (possibly more) but will cut down some on two power heads I'll be using. It is still a bit of a guess as two of the under gravel filtration risers will be air driven so their flow rate is, at best, a close estimate. Most of the water flow will come from the 2 127 gallon/hour power heads but the air driven risers still have to be considered as they push a lot more water than one would think. I'll estimate the flow from the risers that are air driven by filling the tank to an inch or so below the riser head and put a container in the output and time how long it takes to fill. While not exactly accurate this will give me a working idea as to how much water the air is moving. I'll use that as a base and then adjust the power heads to get, at least, close to my goal.

Again @GaryE I would agree on a second filter over just an added pump. To reach the suggested flow rate of 5 turnovers per hour in general the added filter would need to move 667 liter per hour if my math is correct and that would be running the filters at full capacity which is something I never recommend.. Sorry but I'm converting gallons and liters pretty much on the fly so may not be totally accurate as to numbers..

Bottom line is that you have to look at the fish and what they like. As an example it is not good to mix South American Cichlids with African Lake Cichlids as the South Americans like soft water while the Africans like hard water. It is just not a good mix. The same is true with water flow. The Pandas are going to be the main fish and they like fast water. I also want a group of small colorful shoaling fish to occupy the top portion of the tank but have to find a species that also like fast moving water.

In my opinion keeping fish is no less of a responsibility than keeping a dog or cat. Mayhaps fish are even more of a responsibility than a dog or cat as we are taking in a living beastie that is totally dependent on what we do. It is not a privilege for us to have fish, or any other critter, it is a direct responsibility. The way I populate a tank is to pick what I want as the main fish and then pick secondary fish that pretty closely like the same conditions.

@Magnum Man I actually like some algae as I think it gives a tank a more natural. Sadly, with my wanting Pandas and, hopefully, a scud colony even black beard algae won't have much of a chance. LOL! At least I'll be able to extend my light time by a couple of hours.

​

 

[CassCats]

The biggest issue with lack of circulation and "algae" is that cyanobacteria (sometimes called blue-green algae) behaves like algae but is very fond of areas and tanks with limited circulation.

Other algae--true algae--won't care if there's flow or not. All my tanks 55g and larger are all higher flow tanks. I run both canister plus wavemakers.
I have algae thriving in the flow.


The gourami is where I'd think twice over adding too much flow.

Most other fish are often found in areas that have more flow than we realize if you watch wild videos. Its interesting. What many of us consider too much flow in the hobby is often minor flow compared to the wild habitats. You'd be shocked at how much flow even the tiniest of tetras could handle.


That said, tanks also are much smaller than nature so have less room for fish to escape when they want a break, so something to consider with flow rates too.


My suggestion: a low gentle powerhead or small pump on the opposite end of the tank as the filter, towards the bottom area, would allow some circulation without being too much flow for the gourami. Even an airstone on the opposite end could work as well!

That said, if you don't have any cyanobacteria, and you can see some movement in the water even at the far end of the tank away from the filter, you should be okay. Plants do benefit from circulation as well, but the overall health of the tank does. Circulation does not need to equal high flow either.



Algae with flow:

For what it's worth, my tanks have 528gph wavemakers and even the tiny ember tetras are perfectly fine with it. They have areas to rest because scaping allows sheltered areas, but they often come sit out in the flow too. Goldfish tank is larger, has a 1300gph wavemaker there. But no small fish.

 

[OldFishKeeper]

In my limited (65 year) experience, flow rate is only a small part of the algae control equation. I have a 75 US gallon tank with a Fluval 307. It has areas of both high and low flow. It has high intensity lighting for the DFG, Mini in front and medium intensity for Water Wisteria, Val and Swords in the mids and back.

With a good balance of lighting hours, controlling nitrates and regular water changes, algae is not a problem and keeps the otos and cherry shrimp happy.

Guess I am just lucky...

 

[CassCats]

Check these videos out of wild fish in areas that have significantly higher flow than we would think can handle.





And surprisingly, same for angelfish, check this out




Gourami though, are not usually fond of flow and can be stressed by it. That said, three spot gourami are often found in the main channel of the Mekong River and are said to handle some moderate flow, compared to other gourami species.



Volume up for this one, can hear these guys in the video


This shows a little bit of flow, not much, in this habitat for dwarf gourami (very stirred up)



So you can get an idea of what certain fish evolved in and what they can handle. So since you've got gourami, definitely consider keeping flow lower end, but still circulation is important to consider still

 

[fishorama]

I like 2 filters on most tanks 20g & up. But with some areas of lower flow so even current loving fish can have a break if they want. It also allows me to clean 1 filter well without damaging the beneficial bacteria much, if at all.

Algae are often from too long a photoperiod. Some people advocate a "split" light time. I do 6-8 hours of lights on, but get a tiny bit of sunlight through high windows. You can try 3 or 4 hours of lights on, a few hours off, then another 3 hours or so on.

If your lights are on a longer time, you will grow some algae...maybe a LOT! Some fish like to graze on some forms of algae but plan to have to scrape the front glass. Luckily for me my husband does that