I need some advice regarding my 200l planted tank as I may have made too many changes at once and I'd like to catch things before they get even more out of control...
I've had the tank for years but last December I moved it and took the opportunity to completely "redo" the tank. I put in pressurized CO2 controlled by a pH controller, Dennerle Deponit substrate with gravel on top, 125W of lighting (5x 25W tubes) and started using Dennerle's fertilizing regimen.
Then towards the end of August I bought some Alternathera and realized that I was probably lacking in Ca due to stunted growth at tips (water was temporarily very soft out of the tap for some reason). Anyway, that woke me up to the fact that with Dennerle's fert system I had no control over the ferts and couldn't "tweak" things if I thought I needed to so I switched to dosing myself with an order from Greg Watson.
Over a one week period after dropping the Dennerle ferts, I got the parameters to the following:
Fe= 0.2, NO3=10, PO4=1-1.2
GH was at 9 and Kh at 7, temp at 28-29C (discus in tank), pH set to 6.9. 50% water change once a week.
Then in the middle of September, wanting to boost my lighting up for my newly purchased Cabomba furcata and E. Stellata as well as to get more light to my E. tenellus which was struggling, I added another 25W tube to the hood for a total of 150W over the tank (4x JBL Solar Tropic 4,000K 25W and 2x JBL Solar Natur 9,000K 25W).
Continued using KNO3, CSM+B, KH2PO4 and K2SO4 as ferts to keep the levels as above. Would dose around 18mg/l K at water change and then 3-4mg/l K added (through KNO3 and/or K2SO4) every other day.
Suddenly I started noticing that green "fuzz" algae was growing on the front glass quite rapidly. Whereas before I was cleaning the glass once a week at water change this was amazing: I could almost see the d**n stuff spreading on the glass!
I clean it off at lights on and within a couple of hours its back!
First I lowered the photoperiod from 11 hours to 9.5 hours: no perceived difference. So I thought I would try to lower PO4 to 0.5 and NO3 to 5 and keep the Fe and traces up to see if that helped. So at last water change (27th), got the PO4 down to 0.5 and added enough CSM+B to get the Fe back up to 0.2 and KNO3 to get NO3 up to 5-7.5. K2SO4 also added to get total addition of K to total 11mg/l for whole tank (22mg/l in the new water). I also did a major pruning of the tank.
28th added 2ml of CSM+B (of 1tbsp CSM+B in 400ml of RO water solution), effectively adding 0.032 mg/l Fe. Yesterday added 1/4 tsp K2SO4=almost 4 mg/l K. Today added 2ml CSM+B solution.
No noticeable slowdown of this green "dust" algae. It's like a dust and comes off really easy. Can now start to see it on plant leaves as well...
I'm amazed at the speed of this stuff! Literally an hour or two after cleaning the glass I can already see a haze of it back on
So I assume that this may be caused by too many changes at once: adding 25W of light, new fert dosing regimen, phosphates out of whack for my tank, heavy pruning last week, etc. ? The plants are pearling quite a bit but their growth has slowed somewhat.
Do I just need to wait and hope the plants adjust to the new lighting?
Apologies for the length of this! Any and all advice welcome!