Re: Fe as limiting nutrient

[Thomas Barr <tcbiii at earthlink_net>]

> I have always remembered being somewhat inspired reading the original Conlin
> and Sears paper about limiting nutrients and algae. I always thought it was
> cool to be able to measure nutrient levels, find one nutrient that was
> deficient, add the deficient nutrient, and then observe another nutrient
> level decrease as growth of the plants increased because of a balance of
> nutrients consumed by the plants. However, I never really was able to
> observe it firsthand.

PO4 and NO3 are two good examples.
Don't even try iron or traces.

> If I added iron to one of my tanks, the iron levels
> would remain the same after a week. The same with nitrate. The levels would
> not decrease significantly over time. Growth of the plants was OK with the
> strong lights and Co2, but often so also was the algae.

Well unless the fish/critter waste are balanced with N needs of the
plants........this should not likely occur.
 
> discussion with Tom Barr. Since these nutrient amounts were considerably
> more than I had used previously, I hadn't checked nutrient levels in a few
> weeks. Last week when I checked the iron in both tanks it was zero per my
> Hach TPTZ test kit. So I doubled up on the iron that day. The next day, same
> thing: zero Fe, and added another shock of iron. This has continued all
> week. Although I just purchased a 2 liter bottle of Flourish, I was thinking
> that at this rate it would be gone in a short time, so I started using some
> Flourish plus Iron I had since it has a lot more concentration of Fe in it.

So you have learned the Fe lesson. Test kits do not tell you what you need
to know(is the plant getting enough iron?).

> I have gotten to the point where if I dose the 125 gallon tank with 1 capful
> of Flourish plus Fe (.13 ppm) it will go down to about .03 ppm in 12 hours.
> That comes out to 1.8 ppm Fe per week for the 125 gallon tank!, (based on
> 100 gallons of water)...equivalent to 35 capfuls (5 ml each) of Flourish per
> week.

Relax.
Use your eyes, not your kits.
 
> The 75 gallon tank is not as fortunate. I do have the growth similar to the
> 125 but there is still new algae growth. The difference is that I can't
> remove all the algae from the plants in this tank because they are my older
> plants from the previous set up. They had algae on them before, and since it
> doesn't rub off, its hard to prune most of the leaves from the plants. These
> are my non local plants, the exotic ones that I had purchased in the past. I
> can't afford to replace them if I throw them out, like with the 125 gallon
> tank and the local plants.

Get cheap hornwort etc, anything will do.
Once the tank is doing well, phase out the weeds.
 
> One possibility as to why the nitrates have not gone down is that I have
> about sixty local sailfin mollies of all sizes in the 125 gal tank. Perhaps
> they are giving the plants the needed nitrate levels, and preventing the
> nitrates from being exhausted. I was afraid all the fishfood would provide
> too much phosphate, but with the decrease in algae I suspect not.

Old half dead algae covered leaves vs a nice fresh growing plant?
Which will use more NO3? Which will do better against the algae?
 
> Am I doing anything wrong? Anyone have a cheap way to supplement just iron
> (hopefully a chelated form)?

I use Plantex one day and Flourish the next.
 
> I am considerig throwing out the exotic plants in the 75 gallon tank and
> replacing them with Bacopa monneri, which happens to be only locally
> available (from the ditches)aquatic plant at this time (and the Florida
> Invasive plant site considers it a terrestrial). I do like the java ferns
> and Telanthera but I think that you've got to be quite ruthless at the algae
> removal if you don't want it to come back.

Here!Here!
Get that weed in the tank. Moneywort is under rated anyway.

Regards, 
Tom Barr

> 
> Regards,
> Steve Pituch