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Re: Benefits of planted tank for fish
> Date: Fri, 9 Nov 2001 01:50:19 -0700
> From: "T. Mathews Jr." <titus at enel_ucalgary.ca>
> Subject: Benefits of planted tank for fish?
> I assume that many who add KNO3 to their tanks also keep
> fish in those tanks. From this I conclude that regular NO3
> concentrations of around 10ppm must be something that fish can
> thrive in. (Is this correct, BTW? I understand that it would
> depend on the fish, but generally speaking?)
> So, from a fish's benefit perspective, if plants aren't kept
> to get NO3 down to negligible levels, why are they kept? Is
> it because they increase the amount of dissolved oxygen? Or
> perhaps they provide some stability to the water chemistry?
Some of the chemistry is pretty complex and obscure, but the nitrogen stuff is
well-known and very simple. Alelochemicals and strange organics also may be
soaked up by the plants, but the #1 and 2 plant benefits to fish are getting
harmful forms of nitrogen out of the water column and increasing dissolved
Nitrogen has three primary bound forms in an aquarium. Two of those, ammonia
(ammonium) and nitrite, are harmful to lethal, depending on concentration.
Nitrates, OTOH are relatively harmless in concentrations below a few hundred
ppm. The higher oxidation state apparently makes nitrates relatively inert and
slow to do any fish damage. That inert nature also makes nitrate difficult for
the plants to extract, and use as food, but they do eventually use it up.
Pruning plants thus removes harmful products, much as water changes do.
Fish waste is heavy in ammonium/ammonia, and at high pH more is in the deadly
ammonia form. About 50 times as much at pH 8 as at pH 7, as I recall. Nitrite,
OTOH, is harmful at lower pH (6 or below). Ammonium is converted to nitrite by
some of the "beneficial" bacteria in your tank. Other bacteria convert that
into harmless nitrate, eventually, but an "uncycled" tank may suffer a huge
nitrite spike while getting there.
If the pH is high, the ammonia severely burns gills and the ability to get
oxygen is dramatically reduced (gasping at surface symptom). Similar things
happen with nitrites at low pH. Fish (and to a great extent plants) do not
feel pH and don't really care about it as a condition for happy life. pH shock
and a lot of other mythology developed around a lack of understanding of the
chemical effects of pH, particularly with ammonia and nitrites.
Plants are lazy, so they will take the more reactive ammonium and nitrite
forms of nitrogen more readily than they will use nitrates. That has a
powerful water-cleansing effect on the more toxic forms of nitrogen compounds.
As the plants photosynthesize, they give off copious amounts of oxygen, which
further eases any fish with slightly burned gills.
I'm very late to coming to the plants as aesthetic elements to my fishkeeping,
but I have always used live plants as essential companions to my fish since I
started the hobby back in the early '50s. Babies grow up less stunted,
reproduction is improved, and true color of many beautiful fish is never
achieved without the oxygen levels they can produce.
Tank "cycling" has its own fish-store mythology. A growing tank of plants
never cycles, as the plants quickly steal all the ammonium from the bacteria.
It can be stable from day 2. Most of the active bacteria are on the glass and
in the substrate, with some measurements showing only 30%, at most, in the
filter biomedium! The other 70% are distributed all over the tank. [I know.
That doesn't sell a lot of biowheels, but I do like their oxygenating effects,
From experience among the members of the local SFBAAPS, "Amquel" o/e can trap
ammonia but still release it to plants OK, so that's one way to protect the
I don't like it, because I believe plants harbor a lot of rotifers, paramecia,
etc. that the fish graze on. The chloramine removers are deadly to small
inverts, so I avoid them when carbon filtering (cartridge GAC or block, never
in-tank) will do the job. That means my fish get some live foods, whether I
buy them or not.
I use triple-strength "Amquel" for *shipping* fish, as 90% of fish mortality
in transit is ammonia poisoning from improperly "starved" fish poop, either
during travel or upon hitting high pH water when introduced to a new home.
[Plants, in respiration in the dark, should never be shipped in the same bag
with fish, BTW. They will quickly steal all the oxygen.]
Sorry for wandering a bit, but I hope I have conveyed the common sense of
keeping live plants with fish whenever possible. When I had 150 tanks and
smaller jugs and shoe-boxes running, I doubt if I ever had much more than 1 or
2 hospital tanks completely without plants.
I use Petrie dishes to hatch killy and Blue-Eye eggs. I discovered a long time
ago that a sprig of Java moss in each introduced enough infusoria filter
feeders to keep bacteria from harming any healthy fertilized egg. Test it
yourself. A tiny pinch of food in two glasses of water, one with and one
without Java moss. Check the clarity in a couple of days if you want
convincing evidence of what "plant filtering" can do.
Hope that covers it for you T.
Wright Huntley 510 612-1467 - 879 Clara Drive, Palo Alto CA 94303
"You need only reflect that one of the best ways to get
yourself a reputation as a dangerous citizen these days is to
go about repeating the very phrases which our founding
fathers used in the struggle for independence."
-- Charles A. Beard (1874-1948), U.S. historian