Fish stock capacity in a planted tank

branfrog · 07-17-2009, 03:50 AM

I was just watching planted tank vids on youtube and one guy had a pretty nice looking planted tank, didn't look like it was more than 20 gallons, he didn't specify the light watts per gallon (looks kinda low), he uses ferts, but claims he doesn't inject co2 at all...My first thought was that it was probably a new tank and would later break out in BBA alage after a few months...I'm scorned by BBA

..

But then I noticed the tank had a lot of fairly large fish in it +2" and was definitely overstocked per the 1" of fish per gallon rule. This got me thinking, does the 1" of fish per gallon of tank apply to a mid-heavy planted tank?

Given that a tank is cycled with a tolerance to handle large amounts of ammonia, it stands to reason that an overstocked planted tank is a benefit to maximize natural co2 production from the fish; and in essence creates a natural deterrent to BBA growth. Is this right?

Of course, you run the risk, (if for some reason, a good percentage of the plant stock dies), the oxygenation process could fault and the fish would then die of co2 poisoning. But in a well maintained and observed tank, this shouldn't be a problem and the co2 levels should be consistant. let me know if this logic is wrong.

I've been a strict follower of the 1" of fish per gal rule to date, but if this is the case, I would gladly add more Harlequin Rasboras to my current school of 2 and would also gladly notch down my co2 injection as appropriate.

Jay · 07-17-2009, 08:21 AM

Hi Bran...you have a couple of questions and issues brewing there.

The one inch per gallon rule is really a "hand shaky, weak, confusing guideline" used primarily by new hobbyists. The real issues are overcrowding that produces stress from whatever reason...high nitrates, low O2, territories, TDS, etc. etc. Plus the obvious five pound bass in a 10 gallon tank.

The CO2 issue is a little more complex. Remember a tank does not need CO2 injection in order to be heavily planted. A low light tank has approx. 5 ppm of CO2 available just from gas exchange at the surface and a small amount from the critters. This is usually enough for many varieties of plants as long as they have access to Nitrates, GH with a good ratio of Mg and Ca, K and some phosphates.

A good plant mass will suck up lots of nutrients in the tank but a heavy/increasing bio load will at some point become a liability.

Quote:

Given that a tank is cycled with a tolerance to handle large amounts of ammonia, it stands to reason that an overstocked planted tank is a benefit to maximize natural co2 production from the fish; and in essence creates a natural deterrent to BBA growth. Is this right?

IMO no. CO2 from the fish is only minimal, far less that the 4-5 ppm of that is naturally available. BBA is slowed by CO2 in amounts approaching 30 ppm, which is not going to be reached without injection.

Quote:

Of course, you run the risk, (if for some reason, a good percentage of the plant stock dies), the oxygenation process could fault and the fish would then die of co2 poisoning. But in a well maintained and observed tank, this shouldn't be a problem and the co2 levels should be consistent. let me know if this logic is wrong.

It's (the logic) not wrong...you have just drawn a wrong conclusion. There is not enough CO2 produced by critters to get anywhere close to toxic levels. If the plants die out, and you have an overcrowded bio-load it is going to be stress that causes you problems. This is not something that will happen over night. Remember that O2 is difficult to dissolve in water. Plants pearl because the O2 in the water is saturated, and most of the O2 comes from surface gas exchange. Your real danger although remote is the Heterotrophic Bacteria working of dead and decaying plants will deplete your O2.

Well that's my ramble...too much coffee this morning

Jay

branfrog · 07-17-2009, 01:18 PM

Excellent information! thanks Jay!

Whenever I start to speculate and drift from the basics of fish theory, leave it to Jay to set things straight!

Dood, you should teach a college class about planted aquariums!

I'm going to read up on low tech, low light aquariums, it will probably help me to better understand what I am doing in my high tech tank. For a while I've been thinking about starting a separate shrimp tank, perfect opportunity for a low tech!

Alban · 03-31-2010, 03:43 AM

Hello! i have found a lot of useful information from here. Keep up the good work. See you around.

Jay · 04-01-2010, 06:57 PM

We haven seen Bran around for awhile...but please feel free to post and chat anytime.

branfrog · 07-30-2010, 01:33 AM

LOL! I'm Baaacck! I recently had a reverse fish stock problem!

(lost about 50% of my fish stock) So i decided to browse the forums tonight for some inspiration!

This is mostly to do with my war on BBA then eventual exhaustion on the subject to the point where i began to neglect my tank. I can tell everyone for a fact, that dosing hydrogen peroxide then not doing a water change for more than a week will kill your fish...

Due to my neglect, i haven't noticed the fish loss until just this week! ADF is doing fine and thriving! Wonder if hes getting some good snacks off the casualties.

To add to the BBA problem I wanted to add more plant mass, "elephant power" (as jay would put it), so I decided to get some glosso. Had problems with keeping it on the substrate, so i added a desk lamp with an articulated arm and a 6,000k cfl to increase the light intensity in that one spot...created lots o green spot algae, then the glosso formed a very prolific duckweed-esque canopy that would completely cover the surface of my tank every week or so. Long story short, my tank descended into darkness and the bba is still there!

Earlier tonight i decided to break down the tank, sterilize everything, (except the filter), salvage the fish and few non-BBA-infected plants and start all over!

The mopani wood i had is beautiful, mature java ferns and Anubias growing on and in it. But this wood always had the most stubborn swafts of BBA on it, like velvet black fur everywhere, so this is sadly going into the trash. I am thinking my new tank will still be planted, but very bland...

Goldfish Care · 09-18-2010, 02:10 PM

I've been wondering about this same issue. Can you have more fish if you have a planted aquarium. @Jay, thanks for the in depth explanation. It's kind of what my conclusion was too but your explanation helped clarify why.