Contained Carbon dosing in freshwater aquarium.

[markstrimaran]

This is a change of title. From my 5 GPD RFUG. As the ongoing experiment is pushing 20 GPD. As it continues to evolve.

My 75 gallon tank is cycling still and will have the potential to process 100 gallons a day. It uses a fluidized anaerobic, anoxic fine sand media with direct carbon injection.

My 30 gallon tank is working well on sugar dosing the anaerobic canister. I am going to switch it over to vinegar, as the sugar water spoils.

I am going too stack two 75 gallon above each other on a steel stand, the 75 gallon I am building will serve as the "modified sump." for 150 gallons of over crowded African Cichilds.

 

[markstrimaran]

Update.
Nitrates at 5ppm
Flow 20 GPD
Dosing 1 tsp sugar/3 cc vinegar per 2 liters, at 250 ml/day.
Anaerobic canister effluent 2ppm+/-
+1 ORP mv

In my recent drop from 20 + ppm nitrate. I have noticed. That a slight hydrogen sulfide odor begins around +15 mv. Which means the carbon dosage it too high. The effluent will have all the nitrates removed, causing the bacteria to start metabolizing sulfate for oxidation purposes.
I have worked at hazardous H2S work sites. So I can say the amount is very faint. I could see it being a problem for a denitrator that is dosed based on trial and error. Haphazardly.
Best practice would be to run it with a trace of nitrate in the discharge.
I do not think that a ppm of less than 5 , in the aqiarium, is really feasible.
Once the water going in the denitrator is this low, the dosage and flow fluctuations from scum, and head pressure of the drip dosage tank. Makes dialing, in a good ORP mv measurement hard to regulate, with hardware store DIY parts.




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[markstrimaran]

Update.
Tank 5ppm nitrate.
The vinegar is much easier than sugar water. It seems to have a lot more octane. It does not get cloudy after a few days. Which keeps the drip rate constant, less the head pressure loss.
I am still on the same mix of sugar to vinegar, but only dripping about 100 ml/day.
If the ORP gets a little on the +10mv side it is simple to add a little water to the dose tank, to bring it back to optimal. Without adjusting any flow rates.

 

[markstrimaran]

Update
Tank at 15ppm nitrates.
Used only 750ml of dosing all week.
flowing about 5 Gpd.
The slow flow is from me being too busy to adjust it. After I refilled the dosing tank last weekend.
Increased flow to 15 GPD.

The brown diatomaceous algae has mostly gone away. A true purple algae is now growing, the fish have been keeping it very thin.
I am thinking that it is a high alkaline type, still trying to find more information about it.
It looks like salt water coralline. I have read about other African cichlid tanks with similar algae. From videos of Lake maliwai it appears to be growing their as well.

 

[markstrimaran]

Update.
I ddon't know how a coil denigrate can work after 4 months of crud growing inside a 1/4" tube.
I remodeled the 1st chamber as the siphon line was plugging up at anything above 10 GPD.

I glued a 4" pvc pipe to the top of it so I have some thickness. That will hold a taped threaded hole. With 3/8" tubing going into the second canister. Gravity powered with out the pita of a siphon.

 

[markstrimaran]

Update: 30 gallon long, installed needle valve on intake side, as drip regulator was maxing out at 20GPD.

Nitrate 15 ppm
Flow 45 gallons per day.
Dose, 6 cc vinegar 1/2tsp sugar at ? 1000 cc/ day. Too fast too count until dosing tank goes down. At 1800 ml @ 4:15am.
Might crash but Is experimental.
ORP mv was +4 up to +7 now so it's effluent is 0 ppm. The bacteria are keeping up so far.

 

[markstrimaran]

Update,
Any excess vinegar will give false ORP reading. I noticed this on the 75 gallon as I was dosing it.
As it does not have an anaerobic bacteria population built up yet. Probably because it is acidi

After an hour I am only removing 5 ppm from the 45 GPD flow.
So I am back to the low teens in flow. Thinking about using just sugar, maybe vodka.

 

[markstrimaran]

Update:
12 Gpd flow
dosing 4cc sugar per liter at 16 DPM apx 300 ml/d
ORP mv +10.
Test tube nitrates at 0ppm
ORP +2=8 ppm
ORP +6=4 ppm
ORP +10= 0 ppm
Had too recalibrate. ORP mv.

 

[markstrimaran]

My sugar dosing liquid is high alkaline tap water, it has a -negative 35 mv, I added 4 drops of vinegar into a 1/2 cup of it and the ORP was posted +145 mv. I will have too recalibrate for any variations of the dosing mix.
The bacterial culture that use sugar, do not seem use vinegar. So I would be looking at a long cycling time.

Update on the sand filter denitrator 75 gallon.
Nitrates at 50 ppm
Temp 55 F
Seeded the denitrator today. The low water temperature will probably slow it down alot. I figure that if I can get it too reduce nitrate at 55F. Then it should be able to handle 78F all the better.
Biggest problem is getting all the oxygen burned up with the aerobic bacteria.

 

[markstrimaran]

Update.
30 gallon tank
10ppm nitrate
Flow 10 GPD
Dosing 500 ml/D 3 cc sugar per liter.

Replaced the roller valve with a higher flow needle valve.

Replaced dose tank IV Drop counter, with a lower flow, 20 drops per minute. The drop orifice is a lot bigger and should not plug as fast. The old one had a "16" Guage needle as a drip orifice.
Reduced the dosing sugar from 6 cc to 3 cc per liter. It makes it easier to manage, as once the nitrates get lower than 10ppm it is easy to over apply the carbon source.
Which causes hydrogen sulfide to be produced. So far I have only had h2s a couple of times once when the previous filter pluged, and once when the dosing tank was not set right.
Hardly noticeably, but easily fixed by adjusting the flows.

The 75 gallon I think needs more fish "bigger bioload" as the sand filter is not removing enough oxygen yet. Warming it up to 75 degrees would help the oxygen problem also.