Ideal Sponge Filter Flow Rate for a 20G (or general rule)

[Tyler B]

Hey everyone,

I have a 20G tank with the medium sponge filter and it is going well. I got the Tetra 40G air pump because it seemed like it would have enough flow rate, but I found it pumps 1.3 Liter/min which only comes out to ~21 Gal/hour. I've seen that at least 4 times turnover is recommended, so it seems I am way under where you want to be if that's a good metric. I guess they are not rated for standalone filtration.

 

The tank is what I would call decently planted at this point in time

My planned stocking in case it's relevant is:

• 8-10 ember tetras
• 8-10 neon green rasbora (or similar nano fish, not 100% sure yet)
• 1-3 honey gourami (only 1 left when I got it and it seems like you can keep them alone? I could also take it back in case the filtration is not ideal)
• 5 kuhli loach
• cherry shrimp
• misc. snails

 

AQ Advisor shows me that the stocking level is ~100% but the filtration capacity is what is worrying me. I'd probably be changing ~25% water per week.

 

I was just wondering what amount of turnover you use with your sponge filters so I can get a better idea.

[nabokovfan87]

I would recommend starting here.

You can also (recommended) get a gang valve and drop a ziss air stone somewhere in the tank. Depending on what pump you're using this might not be required. It also gives you the flexibility to run a second sponge if you want to try to eliminate dead spots on the opposite side of the tank.  Running one on either side vs. one in the middle for instance.
 

I understand what you're asking in terms of air pump vs. turnover, but there is some other things that come into play. Height of the tank and how much depth of the tank can the pump handle as well.  The pump you have is the one I would've purchased as well so I think your setup and plan is perfectly fine.m

[Widgets]

The turnover rate that is recommended is in reference to water flow, typically used for hang on back (HOB) or canister filters. The sponge filters are spec'd for a range of tank sizes. The video linked above shows how to maximize the airflow for the sponge filter.

@nabokovfan87 has sage advice about running another airstone, or even another sponge filter.

[Tyler B]

On 4/11/2022 at 7:49 PM, nabokovfan87 said:

You can also (recommended) get a gang valve and drop a ziss air stone somewhere in the tank. Depending on what pump you're using this might not be required. 

I'll look into doing this, but what purpose would the air stone by itself serve? Just oxygenate the water and move waste around?

Thanks for the help, thats a relief.

On 4/11/2022 at 7:56 PM, Widgets said:

running another airstone, or even another sponge filter.

Would it be worth it to have another sponge filter in this sized tank? I can go for an air stone on the other side for now.

Ultimately I guess it comes down to me monitoring to make sure nitrates don't go too high between water changes.

Thanks!

[Widgets]

On 4/12/2022 at 4:05 PM, Tyler B said:

Would it be worth it to have another sponge filter in this sized tank? I can go for an air stone on the other side for now.

In my opinion every tank should have two filters. When beeded, one filter can be cleaned on one water change, and the other on the next water change. This gives the beneficial bacteria a chance to recover. A second advantage would be having extra seeded filters available for an emergency situation.

How the tank is scaped will determine if you have room for a second sponge filter. My 10 gallon has 2 sponge filters.

On 4/12/2022 at 4:05 PM, Tyler B said:

I'll look into doing this, but what purpose would the air stone by itself serve? Just oxygenate the water and move waste around?

Exactly. It is better to keep the waste moving around to eventually be sucked into the filter than to have a low flow dead spot where it settles and causes other problems. Either way, there is tank maintenance needed to remove the excess waste, vacuuming and cleaning sponges.

[nabokovfan87]

On 4/12/2022 at 1:05 PM, Tyler B said:

I'll look into doing this, but what purpose would the air stone by itself serve? Just oxygenate the water and move waste around?

Thanks for the help, thats a relief.

it protects the pump and allows you to adjust the flow on everything in the line. whatever "air pressure" is left over is going to go out of the air stone and will result in giving the air pump itself a bit easier lifetime.

On 4/12/2022 at 1:22 PM, Widgets said:

This gives the beneficial bacteria a chance to recover. A second advantage would be having extra seeded filters available for an emergency situation.

If you have a HoB you just take some of your old media on your existing tank,  add it to the new tank and begin to cycle it. In the existing tank you add new media and then off you go.  I basically view it as a 29G needs at least 1 sponge, 55+ tanks need more because they are much longer.  a 40B I would probably run 2 as well. Length of the tank is what determines the filters for me and trying to eliminate dead spots.