Hoejay said:
Thanks for the responses,
CEG could you clarify what you see as beeing unstable CO2. You state that you ran the tank at very high CO2 without fish. Presumably when returning to lower levels of CO2 for the the introduction of fish the plants did not show signs of changes in CO2 levels?
Does this mean that there is a threshold for CO2 levels where stability becomes a problem?
I am just starting up a Jewel Record 96 (about 80ltrs). I've got JBL aquabasis Plus topped with silica grit for the substrate. I plan to dose EI and use pressurised CO2. I've added 2x 24w T5 lights to the standard fit 20w T8 in the hood.
Regards,
Hi,
I like the plan on that Jewel. Yes, if you run fishless you can really go to town with CO2 - no limits whatsoever. Set you timers and open that needle valve throttle. It's like driving on the Autobahn. Exhilarating. 8)
The minute you put fish in though you have to tiptoe round the tulips.
🙁
Fundamentally, stability means the CO2 levels should not fluctuate over the period that the lights are on. It sounds obvious but it's actually easier said than done.
If I could show a graph with "time" shown along the horizontal axis and "concentration" on the vertical axis, then, at lights on, -time=0- ppm should equal 30. Ideally, the graph is flat at 30 all the way across. In order for ppm to be 30 at "lights on" though the gas has to be running before lights on - maybe an hour or more. Barr's idea of an efficient injection system is one in which it takes no more than 1 hour during lights off for the CO2 concentration to rise to 30ppm. There are two practical problems here though>
1. You can't really measure the CO2 accurately. Due to dropchecker response lag you only ever know what the ppm was 2-3 hours ago.
2. If your injection is not efficient then the injection rate required to drive the ppm up to the target level in one hour will be higher than it should be. That often means that the max ppm level will be higher than 30 a few hours later, so you risk getting into the toxicity zone. The only way to adjust for that is to back off the bubble rate and turn the gas on more than an hour before lights on. This problem might be an overstatement for small tanks, but as tank size increases the inertia of getting that much water saturated becomes a pain. The problem is mitigated somewhat if the tank is covered because the water will hold a significant amount of CO2 overnight.
Setting the proper Injection, or bubble rate, is not that easy because the plants are consuming the CO2 which would make that flat line dip as maximum uptake approaches.
If you inject at a rate which gives you higher than the nominal 30ppm, depending on your fish it may still be OK and that means you can shut the gas off a few hours before lights off. There is a certain point during the photoperiod where consumption starts to decrease so turning off the gas early is one of the good things.
So these are the adjustments I had to make when I added the fish. Essentially, I had to get my CO2
timing right by turning on the gas close to two hours before the start of the photoperiod and turning it off 4 hours or so before the end of the photoperiod. The more the plants grew the more CO2 they consumed and the more I had to inch up the injection rate. Also, I time the lights so that only 30% of the light comes on for the first hour or so, which give a bit more wiggle room.
I agree with James about putting in lots of stems in the beginning, even if your scaping plan doesn't include stems. You can always rip them out later, but they are important because they grow rapidly and they get your "ecology" going more quickly. I'm sort of a stem freak anyway so I always follow the guideline as stated by James. The point that I try to get across is that nutrients in a tank are only capable of exacerbating an algae bloom. They cannot
cause it. Regardless of the dosing regimen you use, whether it be PPS, EI, or PMDD you'll get algae if there is a threshold level of ammonia is present. This level is much lower than can be read on your ammonia test kit by the way. Algae in an EI tank looks more abominable because there are more nutrients for the algae to feed on
once it gets started. Algae are opportunists so once spore becomes strand they feed on whatever is available.
Dave, I've read a Barr theory that algae, over millions of years, have "figured" out that when the waters are nutrient rich, inevitably, higher plants would take over. Their niche is actually low nutrient water where there is little chance of higher plant invasion. The theory goes that this is why PO4/NO3 are not algae triggers. Ammonia on the other hand would signal decay and otherwise poor water conditions so this became a trigger for blooms. High nutrient uptake by higher order plants in a tank only means that those plants are healthy and are reducing the ammonia content via their own NH4 uptake mechanism, thus suppressing the algae trigger. If the tank is well established this also means that there is a healthy nitrifying bacteria colony present also consuming ammonia and further suppressing the trigger. When something dies or if a plant becomes unhealthy or if we disturb the substrate, or if we have poor filter maintenance, an ammonia spike is dumped into the water column. If high light is present the algae take immediate advantage.
As far as I can tell, algae can't sense what other plants are uptaking in the tank. They don't care. The spores only look for their trigger. Each species has it's own unique set of triggers but I'm pretty sure ammonia is always in that set.
🙄
Cheers,