# 100 GPH on 40 Gallon enough?



## RisingSun (Jan 5, 2014)

I've got a Rena XP4 hooked up to an Ista Max Mix. The measured flow using a bucket and stopwatch is about 100GPH (freshly cleaned filter). The tank is lightly scaped, 95% of the planting area is only dwarf hairgrass. In one corner, the hairgrass moves very slowly, but there is still movement.

Is this enough turnover and flow for a 40 gallon tank? Thanks!


----------



## Mikeygmzmg (Mar 19, 2015)

In my opinion, yes this is enough. Rena/Filstar make great filters and a 40 gallon should be just fine with one XP4.


----------



## RisingSun (Jan 5, 2014)

Alright cool. I was worried because the filter has a rated flow of 190GPH _WITH_ media. Mine was doing 150GPH without the reactor, and 100 GPH with the reactor. 100 GPH is roughly half of what they said the flow should be _with_ media.


----------



## latchdan (Sep 7, 2007)

Ha im running a xp1 on my 40b lightly stocked bren

Bump: Been fine for a year.. damn phone no edite option


----------



## BBradbury (Nov 8, 2010)

Hello Rising...

If you're willing to remove and replace 50 to 60 percent of the tank water weekly, you don't need heavy filtration. The filter would only be moving water that's already clean. In this case a filter with a gallon per hour rating (gph) of 4 times the volume of the tank in gallons, 160 is plenty. The weekly water change is the real filter, not the mechanical things that hang on the back or are hidden in the cabinet underneath the tank. 

B


----------



## lksdrinkerII (Nov 16, 2015)

Mikeygmzmg said:


> In my opinion, yes this is enough. Rena/Filstar make great filters and a 40 gallon should be just fine with one XP4.





latchdan said:


> Ha im running a xp1 on my 40b lightly stocked bren
> 
> Bump: Been fine for a year.. damn phone no edite option



Dont forget that the OP is running a co2 reactor inline which greatly decreases the flow from the filter. That filter in a stock configuration is likely fine for that tank; but 100GPH is sort of on the lowside of the turnover you'd ideally like to see on a 40 gallon tank. I think its usually recommended to aim for 4-5x turnover rate in a hour which would be 160-200 GPH for a 40 gallon tank.


----------



## latchdan (Sep 7, 2007)

Im running a cerges with mine


----------



## RisingSun (Jan 5, 2014)

What are some "indicator problems" resulting from low flow? I think I'm going to keep it as it is for a few weeks and keep an eye out for indications of insufficient flow.


----------



## latchdan (Sep 7, 2007)

Add a power head for flow

Bump: I use 2 in my 40b


----------



## Freemananana (Jan 2, 2015)

You'll grow algae if the flow is too low. That's the only issue I know of personally.


----------



## Diana (Jan 14, 2010)

You should see some light ripples on the surface. 
The plants should gently sway. 
There should be no area that accumulates debris. This will take time to show up. You might add a power head or circulation pump aimed at this area, when it does show up. Work with the filter, and aim the circulation pump so that the debris is kept moving toward the filter intake.


----------



## WaterLife (Jul 1, 2015)

You sure your Rena Filstar XP4/XL really only gets a flowrate of 100 GPH?!
I've seen these specs listed "for tank up to 265 gallons, flow rate of 450 gph (190 gph with full tubing/accessories/media)".

I haven't owned a Rena canister, but I've heard they are pretty good and I've never seen a canister of that size really only put out 100GPH (even if packed full of media and dirty, well not jam packed/clogged dirty of course).
Maybe yours is worn out or the test was done wrong? Just saying, that I really doubt only 100GPH actual flow rate of a healthy canister/pump (especially if media is clean).

Well anyways, it is generally said a flow rate 5 times the amount of gallons your tank holds is good flow for a typical aquarium. So the 40 gallon x 5 turn over = 200 GPH flow rate.
So you would want a filter/pump rated at 200GPH or more.

But in planted tanks, circulation is more important than a high turnover filter as sometimes the filters don't put out a sufficient current (more GPH does mean a stronger/faster current, but still sometimes it doesn't circulate well enough, like a powerhead vs circulation pump) to effectively circulate all the tank water evenly. Good current and more even circulation is better distribution of nutrients/ferts and co2 (oxygen as well) throughout the whole tank to the plants.


I think with low lying plants (no jungle or other obstructions so flow isn't interrupted/blocked), your canister filter should be sufficient for bioload and circulation (probably not very strong, but should be enough).
But if flow really is that low and you don't have much fish load and are in need of more water circulation, just get a circulation pump (or powerhead as second choice).


----------

