What Biological Filtration For A Brackish Tank With Sump?

[fi_sjo]

Hi all,

Re-visiting my brackish plans again due to moving house. I've got a 180 litre tank with a sump which I would like to use. The tank was originally going to be for marine use but I may cut back in the new pad to save some money.

I was originally going to use an Eheim 2028 with the brackish tank to provide mechanical and biological filtration. With the sump I won't be able to use this filter (if I wanted it in the cabinet).

How do people do biological filtration with sumps for fresh/brackish (< 0.005) water? I don't think I can use living rock, or at least it'd need to die off before colonising with more suitable bacteria based on the salinity? I've seen those reefresh sponges that you can stick in a sump, but they're pretty expensive.

I could always make up a couple of hang-in racks to go in the sump to hold, say, eheim bio media.. but not convinced that's super effective.


Also, do people tend to run phosphate removal media in brackish aquaria?


Many thanks

 

[myenigmaself]

I have crushed coral in bags made of pantyhose in the first section of my sump. Then a refugium that houses plants, algae, snails (mostly Malaysian trumpet but some common pond snails too), and some Amano shrimp. The refugium is pretty low current, allowing the detritus to settle out. Then I have a screen between the refugium and the return chamber. The water going through here is pretty high rate and a lot of algae grows here.

I don't use any other skimmer/phosphate removal media/carbon/etc.

 

[fi_sjo]

I have crushed coral in bags made of pantyhose in the first section of my sump. Then a refugium that houses plants, algae, snails (mostly Malaysian trumpet but some common pond snails too), and some Amano shrimp. The refugium is pretty low current, allowing the detritus to settle out. Then I have a screen between the refugium and the return chamber. The water going through here is pretty high rate and a lot of algae grows here.

I don't use any other skimmer/phosphate removal media/carbon/etc.

Thanks. What kind of plants do you keep in your sump and at what salinity?

 

[myenigmaself]

I have crushed coral in bags made of pantyhose in the first section of my sump. Then a refugium that houses plants, algae, snails (mostly Malaysian trumpet but some common pond snails too), and some Amano shrimp. The refugium is pretty low current, allowing the detritus to settle out. Then I have a screen between the refugium and the return chamber. The water going through here is pretty high rate and a lot of algae grows here.

I don't use any other skimmer/phosphate removal media/carbon/etc.

Thanks. What kind of plants do you keep in your sump and at what salinity?

I'm at SG ~1.004 (although I vary between 3-5). In the sump I've had varying success with java fern, java moss, and anubias. Java fern has done the best, but none of them grow very well due to my weak lighting. I also had really good success with duckweed, but I think you'd have to find a variant that's tolerant of the salinity. I just happened to have some arrive with my java fern.

 

[fi_sjo]

Thanks. What do you think is doing the most biological filtration? The plantlife no doubt will be doing nitrate export, but what about ammonia? Do you think the crushed coral is working as a bio filter?

 

[fi_sjo]

Found some info/videos online yesterday about wet/dry filters. These seem pretty simple to make, wondering how suitable they would be for brackish?

Does anyone know if the de-nitrifying bacteria at SG 0.005 is the same as fresh or salt water? Or something completely different?

I suppose it won't make much difference, it seems both fresh and full marine guys use/have used thse wet/dry systems.

 

[myenigmaself]

Really for biological filtration in a setup like mine the key ingredients are water flow and surface area. The crushed coral and stocking setup provides TONS of surface area in a high flow section of the tank. I would imagine that's where most of the ammonia/nitrite processing takes place. I'm sure there's some going on throughout the tank, including in the substrate of the refugium.

Regarding bacteria and salinity, I don't know if they're different species or sub-species or what, but the bacteria living in marine water cannot survive in fresh and vice-versa. Changing your salinity more than ~0.002 SG will kill off the existing bacteria and new bacteria will have to re-colonize (which may even be a heartier or more salt tolerant variety of the first bacteria, or something completely different acquired from the environment).

Edit:
Thinking about this more, it's more likely that there are a multitude of bacterial species that can perform these chemical processes each suited best for different conditions.

Fun fact: there are more bacterial cells in the human body than there are human cells.