RisenDeep

Umori, the Collector seems to be odd in this deck. Waiting to spend 4 mana to have him reduce the cost of your fishy is useless, even in pioneer. Instead you could use Jiang Yanggu to have all of your creatures with a counter on it produce mana. Deeproot Warrior also seems to not have good synergy with all the other Merfolk you play. I have seen and played this deck also with Jadelight Ranger.

One addition you might consider is The Ozolith to preserve counters if needed

Sheltering Light still has some weaknesses against spells that let creatures get into zero/negative toughness. Something with protection from a color could be more useful

Mistcutter Hydra and Entreat the Angels is quite useless. If you have infinite mana, you want to kill your opponent on the same turn to not get into the risk of have your Angels or Hydra removed from the board. You should cut down Quillspike, same as for the Hydra, it should be your second win-con but not primary.

I don't know in which way Melira, Sylvok Outcast impacts your combo but if it fits from the rules, consider using her as a second Vizier of Remedies

Magistrate's Scepter costs not even a dollar for a playset

Another, propably more reliable option of getting extra turns is Magistrate's Scepter. It is a very old card but was reprinted in Core2019 and so is fully Pioneer legal. I forked a deck I found interesting that makes extensive use of it to have infinite extra turns too.
https://www.mtgvault.com/risendeep/decks/gb-timetravel/

This screams for the Paradise Mantle + Stonybrook Schoolmaster + Intruder Alarm combo

I'd remove Enclave Cryptologist, Streambed Aquitects and Wanderwine Prophets in favor for Patron Wizard, Lullmage Mentor and if you really need Islandwalk: Reef Shaman

The non-creature base of your deck seems a little bit random.

Why are you playing Acuitects Will along with a 4 drop of Spreading Seas?

Turn to Frog is some kind of useless, you don't want to interact witht he opponent in Merfolk Aggro rather than do you own thing and counter stuff that might prevent your plans.

Merrow Commerce is a great support card but only if your creatures benefit from it. I don't see any creature that benefits from it right now and you don't want to block with them, Merfolk is (played right) getting very fast very dangerous so your opponent will try to block you instead.

If you intend to play this deck not too serious, then you could propably run the standard list, means 8 Lords, Aether Vial and so on but you could also run a little bit more relaxed. Stonybrook Banneret is a great card with a lot of combo benefits. Together with Merrow Reejerey you can potentially play your entire hand in one single turn while spells like Sage's Dousing are potential better than Mana Leak with a single Banneret on the table.

Silvergill Adept is pretty usefull too. It is not just a good hit in turn 2 but also provides card replacement in your hand

But I want to drive counters instead because anything in this deck has synergy with them.
Biomancer lets ya traverse through the deck while Shapers let ya draw cards for removing counters and finally Jiang Yanggu makes every Merfolk with a counter to a Birds of Paradise.
Sadly Sage of Fables is not in the format but I think Shapers of Nature do also a great job

Merfolk Seecretkeeper is not very suiteable for this deck. Cut it and insteadd add Silvergill Adept for an additional draw.
Btw. True-Name Nemesis is not Modern legal

Removing Prospector might be a good idea because you don't have something except for Tarfire to play instant. I think it isn't really a ramp if you just exchange your gobbos for mana and then sit on an empty field with nochting except a Chieftain or Warchief. I won't remove Challice because you play it either as a 4 drop or in sideboard.

You could consider adding some prison cards to the sideboard like Ensnaring Bridge so you are protected against Batterskull but can sneak your gobbos or simply hit them into your opponents face

Siren Stormtamer doesn't has synergy with the lords so she becomes a dead card quickly. Cursecatcher is a better option for the tribal aspect and free counter vs paying U for the Siren.

Aquitect's Will is an option but Spreading Seas can render opponents lands harmless, not just transforming them into islands but they also loose all other abilities and types. This is usefull when you for example face against Tron or Scapeshift decks while Will may cause an advantage to your opponent for giving him/her an extra island

Thats because I liked it so I copied it for archiving reasons ;)

At the end its your choice but you shouldn't worry about someone else has had the same idea and posted it to the net. There will always be someone faster or better and crippling a deck just to play something unique isn't worth it I think.

- Wisdom mode off :D

In this case you can opt out Serum Visions, Opt and a Snag for Benthic Biomancer and Silvergill Adept. Vials would be a good extra but if you don't want/can't pay for them, it seems valid to renounce them

Except that Familiar has synergy with Soulcatchers' Aerie

This dosen't seem to be worth to be called control deck. You spend the mana either in casting your lords or in counter/bounce but you can't really do both and if your lords are gone, you don't have any option to win. Go for the aggro foundation or run a control foundation but don't try both, this won't work.

I played this aggro deck successfull for a couple of tourneys
https://www.mtgvault.com/risendeep/decks/merfolk-2/

while Sygg did most of the work (I won 2 - 0 against Jeskai Control, Living End and Black Mill), the small 'control' foundation worked well for me and did the rest (I won 2 - 1 against Tron with Disrupting Shoal and Merrow Reejerey in final, and also 2 - 0 against Simic Infect with a good matchup of Path to Excile)

If you want to run a Merfolk Control variant, I suggest (if not standing mono blue) to run Sygg and Unsettled Mariner, maybe Stonybrook Schoolmaster and/or Summon the School as foundation.

I wanted to try Brineborn Cutthroat in a control deck too because it seems very supportive playing for flash and also getting stronger when casting a counter spell or whatever in an opponents turn. Deeproot Champion also works but it dosen't has Flash and is green so a maybe option.

Grimoire Thief is not just for milling your opponent away, you can also sacrifice it for additional countering. At the same time Surgespanner is very usefull to bounce stuff away from the board while tapping (for example at attack).

Jori En, Ruin Diver is a draw engine in spell battles and grants one free charge per turn so you get more fodder for dominating your opponent.

Lullmage Mentor is a must-have card in Merfolk Control decks. You get a free token for every sucessfull counter spell played and a free counter option for every 7 Merfolk you tap. Works well with Merrow Commerce that itself is a Merfolk-Spell too and also lets ya untap your Merfolk every turn. Try it with Sigil Tracer to copy any spell. This way you can use opponents counter spells against himself.

Last but not least Sejiri Merfolk is a small nasty 2/1 First Strike and Lifelink dude for the small price of just 2 mana if you also control a Plains. Not very difficult when playing Hallowed Fountain or Prairie Stream

Someone a long while ago had a geck like this which even focussed far more on birds. He played a full set of Soulcatchers' Aerie and also Island Sanctuary

Just for couriosity, this is really legal in legacy??

https://www.mtgvault.com/risendeep/decks/frostbite-engine/