Where to begin? In my last update I mentioned the sand had started to look a bit green and generally manky looking (scientific term, lol). At the start of August I noticed a patch of sand at the back of the tank had developed a suspicious brown look to it. It didn't look quite like diatoms and warning bells were ringing so I dusted off the microscope for a closer look.
This is how the sand looked at the back...
...and this is what I saw under the microscope:
So yeah it was dinoflagellates but not a species I had encountered before, this was large cell Amphidinium. Apparently this species is not toxic to livestock but can be much harder to get rid of. The best way to tackle it is to outcompete it by encouraging the growth of diatoms, to do that you have to raise the silicate level so I ordered myself a bottle of Brightwell's SpongExcel. I have since found that this is not the cheapest approach as it's not very concentrated, Waterglass is much most cost effective but at least it would get me started. Apart from the dinos making the tank look dirty nothing seemed to be suffering or dying so I took my time with the dosing, starting off slowly. It's pretty hard to test silica levels with home kits, Hanna do make one but it's aimed at freshwater and doesn't work well for saltwater so I didn't see the point of buying it.
In addition to silica dosing I decided to get a better grip on the nutrient levels. At the beginning of August the nitrate level was around 2.5ppm thanks to dosing NeoNitro but phosphate was still extremely low often registering as 0 on the Hanna ULR. I invested in some NeoPhos and started dosing that too (bonkers really!).
A sand sample taken just over two weeks later looked like this...
There were still dinos present but now I was also seeing some diatoms mixed in as well. I continued to dose silica but still at a lower amount than is normally recommended. The phosphate level had risen to approximately 0.04ppm on the Hanna ULR by the end of August. By mid September I realised that the orignal brown patches at the back of the tank had faded away. I sampled the sand on the 11th September I couldn't find any Amphidinium under the microscope, this was honestly quite a surprise to me as I'd expected to see some still hanging around. So my sand was clean right? Well no, I had replaced one sort of brown for another.
This was the 'new' brown...
I stopped dosing silica and by that time the phosphate was up to 0.06ppm or thereabouts so I decided to hold off dosing any more of that too. By October the sand had progressed from brown to green when cyanobacteria decided to join the party too. It's even got the audacity to smile at me under the microscope!
At the time of typing this the sand is a mix of green and brown. I'm not so bothered about the diatoms because the CUC love it but the cyanobacteria is nasty. So how do I combat green Cyano? I did think about using Dr Tim's Re-fresh but it states on the bottle that it could be harmful to snails and shrimps. I queried this with the manufacturer but they wouldn't elaborate as to how serious the risk was or even how the livestock is affected, is it toxic to them or do they die because of a knock on effect? I'd also rather not use chemicals such as Chemiclean either. So I have an imbalance between the nitrate and phosphate levels right? They currently stand at around 4.5 ppm for nitrate (Salifert) and 0.06-0.09ppm phosphate (Hanna ULR, the test results vary from day to day). Should I keep raising the nitrate (I am still dosing NeoNitrate every day) or try and reduce phosphate, or do both? I did add a couple of new fish at the beginning of September in the hope of addressing the nitrate issue but there was no noticeable effect. Maybe I need to add a few more?
The struggle continues...
Hi, my name is Lisa and I live in Derby, UK. I am a self-confessed reefaholic!