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Biomass - At Capacity or Not?

3K views 19 replies 9 participants last post by  ZuppaDePesce 
#1 ·
How can you tell when your tank is at it's Biomass capacity? Do the weekly nitrate levels tell us this?

I have a hunch I'm there due to the fact that I'm having a problem with high nitrates despite a heavy population of plants. I inject CO2 etc. so it's pretty lush! I'm starting my second year with a planted tank, so I'm still learning.

Rather than get into a description of whats in there, I've posted a picture of my 40 gallon breeder and will gladly answer whatever questions are posted to help me determine if I am at capacity, if necessary.
 

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#4 · (Edited)
First of all, thank you for the replies!

There's probably more than 35 Tetra in there, including 4 new hatchlngs, three Amano Shrimp, two Ottos, two Plecos and one Bolivian Ram!

Ferts: 4 pumps of Easy Green once a week, 2 Seachem fert tabs in two spots once a month. As for feeding, it's TetraMin Plus trop flakes once a day - it's about 1/2 teaspoon . . . they feed in a frenzy and it's all gone in a minute or two.

CO2 Injected - pH @ 6.6 during the day - air pump at night with the pH going to 7.0 at night. KH4, GH 6-8, NO2 0, NO3 - Don't ask. However I've been doing 5 or 10 gallon water changes every few days since last month.

Filtration: Aquaclear-50 (layered from bottom to top) using the stock open-cell sponge, that blue/white filter pad material and some bio media and a Purigen satchel.

You can see a zucchini-round stuck on a plastic plant stand in the front left . . I started that yesterday as a treat.
 
#6 ·
High nitrates can indicate a variety of situations, not just a max bioload.

I think a better indication would be persistent ammonia. If you have zero ammonia, that would indicate a bioload that is below capacity, but having ammonia would suggest you are at or near maximum, especially if it increased with increasing bioload.
 
#7 ·
If both your phosphate and nitrate drop when you change water then climb between water changes that would indicate plants are not able to use them all.

The extra bio media in filter may be contributing to nitrates, it converts ammonia compounds to nitrates, your plants would actually prefer to use the ammonia compounds as their nitrogen source. It’s actually easier and less work for plants to process them over uptaking nitrates.
 
#10 ·
That piece of zucchini was the second time I've done it. I wanted to see if I could lure a large female Amano out in order to get a picture of her egg-engorged underside.

I'm beginning to think that I wasn't changing the water often enough, so I've increased the frequency of that. I'm doing 5-10 gallon water changes a couple of times a week until I get the NO3 down, then I'll be on it regularly.

Additionally, I'm thinking of adding Seachem Matrix in this HOB filter if there's room. If not there are other options.

How does that sound?
 
#18 ·
I've used this website as a general guide to capacity. It seems to be fairly accurate based on what I see in my aquarium: AqAdvisor - Intelligent Freshwater Tropical Fish Aquarium Stocking Calculator and Aquarium Tank/Filter Advisor
That's a pretty cool tool! However, wouldn't having live plants change the capacity of the ecosystem? That tool only accounts for filtration that commercially available filters would provide with a given flow rate and, I suppose, the effect of the bio-media that the filter supports.
 
#15 ·
Personally, I would either add another filter - maybe the AC30 or even another AC50 - or replace the one you have with a larger one. I use the Tidal 75 on my 40B. For the amount of stocking you have I think you could use more filtration than just one AC50. Then, do larger water changes - like 50% - once a week. I only change water every 2-3 weeks, but my stocking is about half of what you have. I do 50-60%.
 
#17 ·
Only way another filter would help is giving more circulation and water flow distribution pushing solid waste around tank and adding a 2nd pickup point for that solid waste in tank. It basically gives you better tank cleanup and increases mech filtration area.

Once that solid waste is captured by mechanical filtration simply clean filter pads to remove that solid waste (organic phosphorus and nitrogen) from tank before bacteria has chance to convert it to inorganic forms -> phosphates and nitrates.

Don’t go to a bigger filter, go to more filters spread around tank for better circulation patterns. Proper filtration is really more about setting up those proper circulation patterns and increasing mechanical filtration than it is about gph and increasing biofilter area.
 
#19 ·
That's a pretty cool tool! However, wouldn't having live plants change the capacity of the ecosystem? That tool only accounts for filtration that commercially available filters would provide with a given flow rate and, I suppose, the effect of the bio-media that the filter supports.
Correct, the stocking calculator doesn't take in the mineral and nutrient consumption of plants. Rapidly growing plants can consume a lot of nutrients while slow growing plants will consume less. Although it might not be possible in your case to get enough plant growth to consume all the nitrate your fish are producing.

However I've been doing 5 or 10 gallon water changes every few days since last month.
In none of the previous posts do I see the size (gallons) of the tank listed. But based on the picture 5 to 10 gallons is not a lot of water for a water change. I do a 50% water change once a week in my much smaller tank. Water changes are important because they remove excess minerals and nutrients. But they also add minerals to the tank the plants need for growth.

Ferts: 4 pumps of Easy Green once a week, 2 Seachem fert tabs in two spots once a month.
Mineral additions from water changes wouldn't mater much if you fertilizer has everything your plants need. But Easy green fertilizer doesn't have calcium or copper. Copper is generally not a problem since most homes have copper pipes. But not all homes have copper pipes. Also calcium is typically present in tap water with magnesium and both are needed by plants.

Your location is listed as Long island NY. Typically the water from this area is quite soft and with limited water changes you might be running out of calcium or magnesium which could be limiting your plant growth. With a GH of 6-8 it is easy to think your CA Mg levels are adequate. But the GH test doesn't tell your home much of each is present. You might has a lot of magnesium and no calcium or a lot of calcium and no magnesium. Or it could be some other nutrient you are short on.

i would suggest gradually increasing your water change amount. If plant growth increases and your nitrate levels drop you may have had a nutrient problem. However if the nitrate levels stay high you might have reached the limits of what you can do in your tank.
 
#20 ·
Correct, the stocking calculator doesn't take in the mineral and nutrient consumption of plants. Rapidly growing plants can consume a lot of nutrients while slow growing plants will consume less. Although it might not be possible in your case to get enough plant growth to consume all the nitrate your fish are producing.



In none of the previous posts do I see the size (gallons) of the tank listed. But based on the picture 5 to 10 gallons is not a lot of water for a water change. I do a 50% water change once a week in my much smaller tank. Water changes are important because they remove excess minerals and nutrients. But they also add minerals to the tank the plants need for growth.



Mineral additions from water changes wouldn't mater much if you fertilizer has everything your plants need. But Easy green fertilizer doesn't have calcium or copper. Copper is generally not a problem since most homes have copper pipes. But not all homes have copper pipes. Also calcium is typically present in tap water with magnesium and both are needed by plants.

Your location is listed as Long island NY. Typically the water from this area is quite soft and with limited water changes you might be running out of calcium or magnesium which could be limiting your plant growth. With a GH of 6-8 it is easy to think your CA Mg levels are adequate. But the GH test doesn't tell your home much of each is present. You might has a lot of magnesium and no calcium or a lot of calcium and no magnesium. Or it could be some other nutrient you are short on.

i would suggest gradually increasing your water change amount. If plant growth increases and your nitrate levels drop you may have had a nutrient problem. However if the nitrate levels stay high you might have reached the limits of what you can do in your tank.
Wow. Thank you for the reply! It's a 40 gallon breeder . . . (can't believe I didn't mention it. Sorry.)
 
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