Re:algae issue 120 gal

[Thomas Barr <tcbiii at earthlink_net>]

> My tank stats are 120G, 2x250w 6500K MH (Iwasaki -1 year old
> bulbs) - 16" above water surface, profile substrate, CO2
> injection.  Fertilizer is TMG (75ml week), 1/2 tsp KNO3 2x
> week, 1/8 tsp KH2PO4 2x week and 2 1/2 tsp K2SO4 1x week.
> 30% H2O change every week.  PH 6.4-6.8,  5 dKH.  One note is
> that the TMG is about a year old as I got a gallon of it
> when I ordered it.

Light/old TMG not likely the issue. Split the TMG dosage over 2x a week or
3x a week. KNO3 seems light.

Large variation in the pH and hence the CO2. While still in good ranges it
might be excessive for fish etc. Try and keep it at 6.7 to within 0.1 units
during the day light cycle.

Try doing large water changes also. Start with a big 50-60%. Get rid of the
muck and algae, dirt etc.
Use a net to get out what you can first, then trim, then scrub off any algae
etc. Net one more time then do a large water change and vacuum up the dirt.

You might change the flow direction , spray pattern etc in the tank to psh
the dirt to one area etc. Once the tank gets going well, the dirt issue goes
away as the tank balances out more.
 
> For what its worth to others, I would never again put so
> much light over a tank or use profile.

Well, folks listen real good afterwards:-) I was that way, I try to steer
folks the right way but folks often need to go down the hard path first. I'm
no different.

 Next time, I bite
> the bullet and get flourite and maybe only 3w/g.  For all
> the cash I have put into this, I have not been satisfied
> with the results.

You can change the substrate later. You can also remove some of it and mix
it with heavier sand.

Now this might be the look you are after, but plant the substrate fully and
then you don't have to see it.

Sand's cheap and you can/might replace it anyway. It'll help keep the plants
down and aid in replanting.

The light issue can be dealt with I think if you increase water changes,
alter the nutrient routine some and stabilize the CO2 during the light
period.

You might feel far off but it's not that bad.
A few little changes really is all that's needed. A little elbow grease for
a couple of three weeks and you should be able to have the tank on track and
where you want it.

Clean the tank well for 3 weeks and do those large water changes. Get the
CO2 set right. Change the mixing/flow of the tank's water. Change the
KNO3/TMG routine. You might need more KNO3, each 1/2 teaspoon is adding
about 4ppm of NO3 each time, not much .......one two's day worth of NO3 for
a high light tank.

PO4 and K are fine.

>  My previous tank (55g) was a much more
> satisfying experience.  It used 4x40w philips ultralumes in
> shop lights and has gravel and could grow absolutely
> anything.   My current tank has a problem even growing
> hygro. :(  Its a wonder I am still sticking with this..
> 
> Bummer.

It's a bigger tank and getting the nutrients, CO2 and flows well mixed
become more and more important on increasingly larger tanks.

Regards, 
Tom Barr