Ongoing issue with Nitrite

[SpotOn88]

Current set up:

Fluval Roma 125 litre tank - Soft water south american set up (with the exception of the plants)

Fluval 206 external filter

Temp 25 degrees celsius
pH 6.4
dKH 0
dGH 1

Ammonia reading 0
Nitrite reading 0.07
Nitrates - cannot recall figure but reading was safe

Current stock

14 x Dwarf Pencil fish
4 x juvenile F1 Dicrossus Foirni (no bigger than 2.75 in length at the moment)
10 x Adolfo Cory (7 x adults & 3 x juveniles no bigger than 3.5 cm)

Tank is mature and has been running for 18 months.. substantial amount of driftwood within tank as well as what I would describe as a moderately planted set up with plenty of water wisteria floating at the top and numerous pieces of microsorum/anubias dotted in between bits of driftwood etc

The issue I have is that I cannot get a 0 reading on nitrite.. I am aware that this possibly as a result of not doing enough water changes (I've been doing a 25 litre water change per week split into 2 x 12 litre water changes every 3rd/4th day) so perhaps I need to up this slightly.

All fish seem happy, healthy and in good condition so I don't believe the nitrite reading is affecting the fish but I am interested to hear what everyone else thinks?

Cheers

 

[dw1305]

Hi all,

Fluval Roma 125 litre tank - Soft water south american set up (with the exception of the plants)..... Fluval 206 external filter
Ammonia reading 0
Nitrite reading 0.07
Nitrates - cannot recall figure but reading was safe......
Tank is mature and has been running for 18 months.. substantial amount of driftwood within tank as well as what I would describe as a moderately planted set up with plenty of water wisteria floating at the top and numerous pieces of microsorum/anubias dotted in between bits of driftwood etc.........The issue I have is that I cannot get a 0 reading on nitrite.. I am aware that this possibly as a result of not doing enough water changes (I've been doing a 25 litre water change per week split into 2 x 12 litre water changes every 3rd/4th day) so perhaps I need to up this slightly.

All fish seem happy, healthy and in good condition so I don't believe the nitrite reading is affecting the fish but I am interested to hear what everyone else thinks?

I wouldn't worry, it all sounds fine.

Test kits are pretty inaccurate. It is easier to test for NO2- than NO3- (some nitrite compounds are coloured and insoluble), but I wouldn't rely on them.

If you ask on other forums they will tell you that your biological filtration is compromised by your lack of carbonate hardness (dKH) this is true to some degree, but we now know that Nitrospira and Nitrotoga spp. bacteria are much more important than was realised, and they are less constrained by low pH and hardness. A reference would be

"Hüpeden J, Wegen S, Off S, Lücker S, Bedarf Y, Daims H, Kühn C, Spieck E. 2016. Relative abundance of Nitrotoga spp. in a biofilter of a cold-freshwater aquaculture plant appears to be stimulated by slightly acidic pH. Appl Environ Microbiol 82:1838–1845".

The conversion of ammonium (NH4+) to nitrite is largely performed by <"Archaea">, and again the same applies to them, they are much more tolerant of low pH and carbonate hardness than the bacteria that were assumed to carry out this role.

If the filter has a lot of filter media in it, and particularly media that might clog easily like fine sponge or floss? I'd remove them. There is a slight possibility that the media may be anaerobic if flow speeds are really slow in the filter. Because you have plants you don't need the anaerobic reduction (denitritification) of NO3 to occur.

cheers Darrel

 

[SpotOn88]

Appreciate the detailed reply

I will continue to monitor but as stated all seems well at present

Cheers