so the tank has been looking great for a few months now. explosive growth requiring pruning every week. its exactly as i had hoped it would become, except there is now an outbreak of staghorn algae. it started on the leaves of my onion plant about 6 weeks ago. it was very minimal and not at all a problem. i would just pick off the tiny little pieces and the return growth would be extremely slow.
its now taken over half the tank. i slipped on water testing and came to realize that my nitrates had become non existent. apparently the waste from fish was not sufficient to provide nitrates. i'm hoping that was the cause and would appreciate it if anyone could confirm this theory. i have since started dosing with liquid nitrogen. however, this seems to be a poor method and the plants seem to be absorbing it almost as fast as i put it in. i know the previous stated methods of overdosing ferts and changing 50% water weekly. unfortunately i really dont want to start that. i like testing water and it has been effective. i just miscalculated the use of nitrates from the extensive growth of the plants. i suppose now i need help with two things. is the lack of nitrates the cause and how the heck do i get rid of this aweful stuff without sacrificing half of my plants.
or will the continued dosing of nitrates and keeping things back in balance just eventually force the algae to die off?

Most algae will live long and productive lives in an aquarium with just enough nutrients and light to fill their needs. And, that amount of nutrients, at least, is less than the plants need. So, getting rid of staghorn algae requires physically removing what is in the tank, or killing it in place, using Excel or H2O2, then making sure the plants have an abundance of the nutrients they need, so the algae is never triggered to start growing again.

In my opinion you are going to continue to have algae problems if you rely on test kits to keep just exactly what nutrients the plants need in the water, without any excess. First, the hobby test kits most of us can afford are not very accurate, and must be calibrated often, using water with known amounts of the nutrient being tested for in the water. Second, the exact amount of nutrients needed isn't a constant - it depends on how much plant mass you have, and how fast it is growing, which depends on the light intensity and how much of all of the needed nutrients you have, including carbon dioxide.

I assume you prefer the water testing approach because you enjoy that part of the hobby. If so, that is probably the best method for you. The EI method would be too simple to appeal to you.

yes i enjoy both chemistry and biology to a great extent. i monitor the tests regularly and am quite certain that my nitrate and phosphate kits are quite accurate. the only thing that has changed recently is the sudden drop off of nitrates which i attribute to the extensive growth of the plants. i would also like to assume that is the cause of the staghorn algae. if not then i am at somewhat of a loss. its too soon to tell, but i think the staghorn algae is now somewhat dormant after heavy dosing of nitrogen in addition with the normal dosing of trace, potas and phosphorous. i was not previously dosing nitrogen as the demand for it was met by water changes, my tap water contains approx 5ppm of nitrate, fish waste and food. i believe it was my mistake of not closely watching the nitrates which caused the outbreak. there is no other trace of any other types of algae except a very small amount of green spot algae on the glass which seems to grow very slowly and is quite managable. one thing i have not understood on this forum is the 50% weekly water change. how do you accomplish that properly. i do not feel comfortable dumping 25 gallons of water into the tank straight from the tap without it being at the exact proper temperature and being dechlorinated first.

One difference between a scientist and an engineer is that an engineer looks for things that work as he wants them to, and only secondarily wonders about the science behind that. A scientist looks at the science first and rarely ponders whether something will work ok. (You can probably guess that I am a retired engineer.) So, something that works very well is removing half of more of the water from the aquarium, adding a dose of Prime to the remaining water that is a full tank dosage, then adding tap water to refill the tank. It also works very well to use your finger as a thermometer to match the replacement water's temperature to the tank water temperature. I used to use just cold water for water changes, but when I did that I limited my changes to about 25% of the tank volume. That worked well too. I don't know why this technique works, but I assume it is because fish are accustomed to sudden changes in water conditions that occur when it rains hard.

We also wait until the tank is refilled with tap water before we add a GH booster, if needed, and that has to be causing the fish to go from good GH to low GH and back to good GH very rapidly. Again I don't know why it doesn't harm the fish.

What happens if you add more and more plant biomass, then the NO3 decline?

Hardly any more plant growth/biomass addition.

What happens if the plants really get limited via N?
They cannot take up NH4 either................they do not produce as much O2..........bacteria also do not take up as much NH4 to covert to NO3.........

Get in there and prune and/or add more CO2/NO3/PO4 etc.

Excel ought to kill what's there.
Clean your tank often and especially after disturbing the sediment.

Careful with Engineer and Biologist comments, I'm both


Regards,
Tom Barr

if i owned a home rather than renting an apartment then i would create a system integrated with the home plumbing system to allow for easy water exchange. i currently have a system in place right now that is quite convenient, however the holding tank is very small because of limited space. i can understand how the minor fluctuations in temp and very brief exposure to chlorine is probably not that harmful to my fish, but this is actually the first time i've had a very stable tank with extremely healthy fish and i'm quite nervous about screwing that up. so you guys are honestly saying, get the tap water close to temp by feeling it, dump prime in the tank at the amount required for the given aquarium total volume, and fill it with a hose? that surely would be quite easy. now do me a favor, figure out how to do that for my reef aquarium.. :-)

I've got a little bit of what I think is staghorn, it's slow going since I'm currently running very low light. I was wonding what it was doing on a few plants but picked off the pieces that annoyed me. Hopefully it wont become an epidemic, but if it does I can refer to this thread.

i followed toms and vaughns advice and it looks like the algae is under control again. deciding not to prune my plants to death, there is still a small trace of the stuff on some leaves. i've increased my fert dosing heavily and my plants are now growing like weeds again. as soon as they seem to have fully recovered from the heavy pruning i will remove the remaining leaves that still have the algae. my problem was multistaged. there was excessive growth and i didnt increase my dosing to cover the new plant growth. i could have avoided the whole situation by keeping the tank tidy in the first place by following toms advice and keeping the plants pruned well. now i just have to figure out what to do with these crazy 3 foot tall swords attempting to grow through my glass canopy. :-)