macroalgae declining(?)

[eleodes]

i have set up two connected tanks as "planted saltwater" with a bunch of different seaweeds. i intend to also add turtle grass. for a while everything was growing vigorously, but it seems to have all tapered off and a couple of species are actually dieing back. one of the Halimeda is still growing pretty good. the newer tank has a 6" deep sand bed. nitrates have always tested s "0", but i am wondering if all of that substrate is really sucking out all of the nitrate and leaving the seaweed with nothing.

should i try fertilizing somehow? maybe by overfeeding fish(?).

 

[bluenassarius]

i keep alot of fish in my tank to keep the bioload up for the macro and they seem to respond well.

 

[eleodes]

that had ocurred to me, but the fish are already sort of crowded. i have a damsel and a wrasse that are both really pugnacious.

 

[Samala]

I would also either fertilize to keep macroalgae density high.. or add more fish. You could source out nitrogen to add, along with some basic micronutrient mix and possibly phosphate if you intend to keep bioload low, or feedings small. If you go this route I would recommend some of Seachem's Fluorish line made for freshwater planted aquariums.. I'm using these with success in place of mixing up my own stuff. Err on the side of dosing nitrogen and micronutrients though, particularly iron with macroalgae since we have some anecdotal evidence that they tend to go to zoospore stage less often if given enough iron.

Testing nitrates at zero could be both good and bad. In a tank full of thriving macroalgae a nitrate test of zero would indicate more that the amount of nitrogen being produced is about equal to what the macroalgae require to grow. In a tank of declining macroalgae.. like yours.. a zero reading for nitrogen (ammonia, trite and trate) would indicate more that you simply dont have enough to fuel the macroalgae's growth and survival. Shoot for a NO3 reading of about 5-10ppm.. that's what I'm holding mine at as this should be low enough for most fish to put up with. In freshwater people recommend from 10-20ppm.

Oh.. and I am inclined to agree with you that your DSB.. as a 6" sandbed without seagrass would effectively become.. could easily be competing with your plants/algae for nitrogen sources. Just as I think that live rock in the average reef system competes for nitrogen sources.

>Sarah

 

[eleodes]

thanks Sarah. i am going to give the Seachem freshwater fertilizer a try. there's actually somebody at the lab with planted freshwater who can gift me a little bit of that so i can see what it does.

 

[Samala]

Arent labs great? A professor downstairs run his own reef, I've got seagrass and then theres always the stinkin zebrafish. Just an FYI, there are several variations on the Seachem ferts.. there's Fluorish, which is all the micronutrients and a leetle bit of nitrogen and phosphorus, theres each of the macronutrients alone Fluorish Nitrogen, Fluorish Potassium, Fluorish Phosphate.. and they also make a Trace and a Iron supplement if you want to control micronutrients a little better.

I'd also start with just straight up Fluorish.. and see ifyou get any response. Then you'll most likley have to include some nitrogen to get the nitrate levels to sit where you want. Nice thing about these products is they are relatively inexpensive. If you really want to shave corners you could mix up your own ferts from straight chemicals. Places like www.gregwatson.com are a decent source for them to the public. Good luck with it!

>Sarah